| Internet Information Services

[This is preliminary documentation and subject to change]

# Glossary

### A B C D E F G H I J K L M N O P Q R S T U V W X

Select the first letter of the word from the list above to jump to appropriate section of the glossary.

# A

access control
The mechanisms for limiting access to resources based on users' identities and their membership in various predefined groups. Access control is used typically to control user access to network resources such as servers, directories, and files.

access control list (ACL)
A list that indicates which users or groups have permission to access or modify a particular file; the Windows discretionary access control list (DACL) and system access control list (SACL) are examples of access control lists.

ACL
See access control list.

Active Directory Service Interfaces (ADSI)
A COM-based directory service model that allows ADSI-compliant client applications to access a wide variety of distinct directory protocols, including Windows Directory Services and Lightweight Directory Access Protocol (LDAP), while using a single, standard set of interfaces. ADSI shields the client application from the implementation and operational details of the underlying data store or protocol.

Active Group, The
A standards organization, under the auspices of The Open Group, which is an open, customer-driven steering committee responsible for the ongoing development and management of ActiveX technologies and licensing.

active script
A script that can be implemented in various languages, persistent formats, and so on, that can interact with other ActiveX Controls.

active scripting
A Microsoft technology that uses COM to run third-party scripts in Microsoft Internet Explorer without regard to language and other elements of implementation. See also Active Server Pages; Automation; Component Object Model component; script; scripting engine.

Active Server Pages (ASP)
A server-side scripting environment that can be used to create dynamic Web pages or build Web applications. ASP pages are files that contain HTML tags, text, and script commands. ASP pages can call Component Object Model (COM) components to perform tasks, such as connecting to a database or performing a business calculation. With ASP, the user can add interactive content to Web pages or build entire Web applications that use HTML pages as the interface to your customers.

ActiveX
An umbrella term for Microsoft technologies that enable developers to create interactive content for the World Wide Web. A set of language-independent interoperability technologies that enable software components written in different languages to work together in networked environments. The core technology elements of ActiveX are the Component Object Model (COM) and distributed COM. These technologies are licensed to The Open Group standards organization, and are being implemented on multiple platforms. See also Component Object Model; Common Gateway Interface; distributed COM; Java.

ActiveX Controls
Reusable software components that incorporate ActiveX technology. These components can be used to add specialized functionality, such as animation or pop-up menus, to Web pages, desktop applications, and software development tools. ActiveX Controls can be written in a variety of programming languages including C, C++, Visual Basic, and Java.

ActiveX Data Objects (ADO)
A high-level data access programming interface to an underlying data access technology (such as OLE DB), implemented by using the Component Object Model (COM).

activity
A collection of COM objects that has a single distributed logical thread of execution. Every COM object belongs to one activity.

Address Resolution Protocol (ARP)
A TCP/IP protocol for determining the hardware address (or physical address) of a node on a local area network connected to the Internet, when only the IP address (or logical address) is known. An ARP request is sent to the network, and the node that has the IP address responds with its hardware address. Although ARP technically refers only to finding the hardware address, and Reverse ARP (RARP) refers to the reverse procedure, the acronym ARP is commonly used to describe both. ARP is limited to physical network systems that support broadcast packets. It is defined in RFC 826. See also Reverse Address Resolution Protocol; Transmission Control Protocol/Internet Protocol.

ADO
See ActiveX Data Objects.

ADSI
See Active Directory Service Interfaces.

ADSI Provider
An application that makes itself available to ADSI client applications by providing an ADSI implementation.

agent
In client/server applications, a process that mediates between the client and the server. In Simple Network Management Protocol (SNMP), agent information consists of comments about the user, the physical location of the computer, and the types of service to report based on the computer's configuration. See also catalog agent.

aggregation
A composition technique for implementing component objects whereby a new object can be built by using one or more existing objects that support some or all of the new object's required interfaces.

alias
A name that maps part of a URL to a physical directory on the server. In general, an easily remembered name used in place of an IP address, directory path, or other identifier; also called a friendly name. See also host name; virtual directory; virtual server.

American National Standards Institute (ANSI)
A voluntary, nonprofit organization of U.S. business and industry groups formed in 1918 for the development of trade and communication standards. It provides area charters for groups that establish standards in specific fields, such as the Institute of Electrical and Electronics Engineers (IEEE). ANSI is the American representative of the International Standards Organization and has developed recommendations for the use of programming languages including FORTRAN, C, and COBOL. Standards approved by ANSI are often called ANSI standards (for example, ANSI C is the version of the C language approved by ANSI). See also ASCII; ASCII character set; ASCII file.

American Standard Code for Information Interchange (ASCII)
A coding scheme using 7 or 8 bits that assigns numeric values up to 256 characters, including letters, numerals, punctuation marks, control characters, and other symbols. ASCII was developed in 1968 to standardize data transmission among disparate hardware and software systems and is built into most minicomputers and all personal computers.

annotation file
For the FTP service, a summary of the information in a given directory. This summary appears automatically to browsers.

Anonymous File Transfer Protocol (anonymous FTP)
Makes it possible for a user to retrieve documents, files, programs, and other archived data from anywhere on the Internet without having to establish a logon name and password.

anonymous-only logons
Allows remote access by the IUSR_computername account. Remote users can connect to that computer without a user name or password, and they have only the permissions assigned to that account. Anonymous access is typically used for Internet sites.

ANSI
See American National Standards Institute.

Apartment model multithreading
The Component Object Model (COM) supports a form of multithreading called the Apartment model. The apartment is essentially a way of describing a thread with a message queue that supports COM objects. Apartment model multithreading enables multiple application threads-one for each apartment-to be managed by COM.

Apartment thread
A thread used to execute calls to objects of components configured as "Apartment threaded." Each object "lives in an apartment" (thread) for the life of the object. All calls to that object execute on the Apartment thread.

API
See application programming interface.

applet
A small piece of code that can be transported over the Internet and executed on a client's computer. This term is frequently used to refer to such programs in the form of embedded inline objects in HTML documents on the World Wide Web.

application
A computer program, such as a word processor or electronic spreadsheet; or a group of Active Server Pages (ASP) scripts and components that perform such tasks.

application programming interface (API)
A set of routines that an application uses to request and carry out lower-level services performed by a computer's operating system. Also, a set of calling conventions in programming that define how a service is invoked through the application.

application root
The root directory for an application; all directories and files contained within the application root are considered part of the application. Also called an application starting-point directory.

application scope
A way of making data available to all users of an application from all pages of a Web application. A variable or an object instance is given application scope by storing it in the Active Server Pages (ASP) application object. Application scope is useful for global data, such as a global counter.

argument
A constant, variable, or expression passed to a procedure.

ARP
See Address Resolution Protocol.

array
A list of data values, all of the same type, any element of which can be referenced by an expression consisting of the array name followed by an indexing expression. Arrays are part of the fundamentals of data structures, which, in turn, are a major fundamental of computer programming.

ascii
In an FTP client program, the command that instructs the FTP server to send or receive files as ASCII text. See also ASCII.

ASCII
See American Standard Code for Information Interchange.

ASCII character set
A standard 7-bit code for representing ASCII characters by using binary values; code values range from 0 to 127. Most PC-based systems use an 8-bit extended ASCII code, with an extra 128 characters used to represent special symbols, non-English language characters, and graphic symbols.

ASCII file
Also called a text file, a text-only file, or an ASCII text file. An ASCII file contains characters, spaces, punctuation, carriage returns, and sometimes tabs and an end-of-file marker, but it contains no other formatting information.

ASP
See Active Server Pages.

ASP buffering
Functionality of ASP that temporarily stores all output generated by a script until script execution is complete, then sends it to a client.

associating
See file name extension mapping.

asynchronous transfer mode (ATM)
A network technology capable of transmitting data, voice, video, and frame relay traffic in real time. Data, including frame relay data, is broken into packets containing 53 bytes each, which are switched between any two nodes in the system at rates ranging from 1.5 to 622 Mbps. ATM is defined in the broadband ISDN protocol at the levels corresponding to levels 1 and 2 of the ISO/OSI model. It is currently used in local area networks involving workstations and personal computers. See also Integrated Services Digital Network; International Organization for Standardization Open Systems Interconnection model.

asynchronous transmission
In modem communication, a form of data transmission in which data is sent intermittently, one character at a time, rather than in a steady stream with characters separated by fixed time intervals. Each transmitted character consists of a number of data bits (the character itself) preceded by a "begin character" signal called the start bit, and ending in an optional parity bit followed by 1, 1.5, or 2 "end character" signals, called stop bits.

ATM
See Asynchronous Transfer Mode.

atomicity
A feature of a transaction considered or guaranteed to be indivisible. Either the transaction is uninterrupted, or, if it fails, a mechanism is provided that ensures the return of the system to its state prior to initiation of the transaction.

attributes
In a database record, the name or structure of a field. The size of a field or the type of information it contains would also be attributes of a database record. In markup languages such as Standard Generalized Markup Language (SGML) and HTML, a name-value pair within a tagged element that modifies certain features of that element.

auditing
The process an operating system uses to detect and record security-related events, such as an attempt to create, access, or delete objects such as files and directories. The records of such events are stored in a file known as a security log, whose contents are available only to those with the proper clearance. See also security log.

authentication
The process by which the system validates a user's logon information. A user's name and password are compared against an authorized list, and if the system detects a match, access is granted to the extent specified in the permission list for the user.

authentication certificate
See certificate, digital.

authorization
In relation to computers, especially to remote computers on a network open to more than one person, the right granted to an individual to use the system and the data stored on it. Authorization is typically set up by a system administrator, Web master, or site owner and checked and cleared by the computer. This requires that the user provide some type of identification, such as a code number or a password, that the computer can verify against its internal records. Also called permission or privilege.

automatic directory listing
Providing a directory listing by default when a URL without a file name is received; also called directory browsing.

Automation
A COM-based technology that enables dynamic binding to COM objects at run time. Automation was previously called OLE Automation and ActiveX Automation.

Automation object
An object that is exposed to other applications or programming tools through Automation interfaces.

# B

bandwidth
The capacity of the transmission medium stated in bits per second (bps) or as a frequency (Hz). Generally, a higher bandwidth number indicates faster data-transfer capability. In communications, the difference between the highest and lowest frequencies in a given range. In computer networks, greater bandwidth indicates faster data-transfer capability and is expressed in bits per second (bps).

bandwidth throttling
Setting the maximum portion of total network capacity that a service is allowed to use. An administrator can deliberately limit a server's Internet workload by not allowing it to receive requests at full capacity, thus saving resources for other programs such as e-mail.

Basic authentication
An authentication protocol supported by most browsers, including Internet Explorer. It is a method of authentication that encodes user name and password data transmissions. Basic authentication is sometimes called clear-text authentication because the Base-64 encoding can be decoded by anyone with a freely available decoding utility. Note that encoding is not the same as encryption. See also Integrated Windows authentication; encryption.

baud
A measure of data transmission speed. Commonly used to refer to the data transmission speed of a modem.

BIND
See Domain Name System.

binding
The way in which Microsoft Visual Basic code uses Automation to access objects in another application. See also Automation; static binding; dynamic binding.

Bits per second (bps)
The speed at which data bits are transmitted over a communications medium, such as a transmission wire or a modem.

Boolean
Of, pertaining to, or characteristic of logical (true or false) values. Many languages directly support a Boolean data type, with predefined values for true and false; others use integer data types to implement Boolean values, usually (although not always) with 0 equaling false and "not 0" equaling true. Queries with Boolean operators (AND, OR, NOT, and NEAR) are referred to as Boolean queries.

Boolean expression
An expression that yields a Boolean value.

Both-threaded
A component that supports Free- and Apartment-threading models. See also Apartment thread.

broken link
A reference to a resource that cannot be located because the URL is not valid, the resource the link points to doesn't exist, or the server containing the resource is busy or is having other technical difficulties.

browser
Also called a Web browser. A client interface that enables a user to view HTML documents on the World Wide Web, another network, or the user's computer; follow hyperlinks among them; and transfer files. One example is Microsoft Internet Explorer.

bulk data encryption
The encryption of all data sent over a network. See also encryption.

business rules
The laws, regulations, policies, and procedures that are encoded into a computer system. Also known as business logic.

bytecode
The executable form of Java code that executes within the Java virtual machine (VM). Also called interpreted code, pseudo code, and p-code.

# C

CA
See certification authority.

cache
A special memory subsystem in which frequently used data values are duplicated for quick access. A memory cache stores the contents of frequently accessed RAM locations and the addresses where these data items are stored. When the processor references an address in memory, the cache checks to see whether it holds that address. If it does, the data is returned to the processor; if it does not, a regular memory access occurs. A cache is useful when RAM accesses are slow compared with the microprocessor speed, because cached memory is faster than main RAM memory.

call
To transfer program execution to some section of code (usually a subroutine) while saving the necessary information to allow execution to resume at the calling point when the called section has completed execution. When a subroutine call occurs, one or more values (known as arguments or parameters) are often passed to the subroutine, which can then use and sometimes modify these values.

callback function
A function provided by IIS that allows an ISAPI extension or filter to access IIS services.

caller
A client that invokes a method of an object. An object's caller isn't necessarily the object's creator. For example, client A could create object X and pass this reference to client B, and then client B could use that reference to call a method of object X. In this case, client A is the creator, and client B is the caller.

catalog agent
An automatic software program that periodically opens all files in a designated set of directories and indexes their contents; also called a link crawler.

certificate, client
A digital certificate that functions in a way similar to a driver's license or passport. Client certificates can contain detailed identification information about the user and organization that issued the certificate. See also certificate, digital.

certificate, digital
An encrypted file, containing user or server identification information, that is used to verify identity; also called an authentication certificate. When issued to users, a digital certificate is called a client certificate. When issued to a server administrator, it is called a server certificate. See also key pair; certificate, client, encryption.

certificate revocation list
A document maintained and published by a certification authority (CA) that lists certificates that have been revoked by the certification authority. See also certification authority.

certification authority (CA)
An entity that issues, manages, and revokes certificates.

CGI
See Common Gateway Interface.

class
In Microsoft Visual Basic Scripting Edition (VBScript), the formal definition of an object. The class acts as the template from which an instance of an object is created at run time. The class defines the properties of the object and the methods used to control the object's behavior. See also Microsoft Visual Basic Scripting Edition.

class factory
An object that implements the IClassFactory interface, which allows it to create objects of a specific class.

class ID (CLSID)
A universally unique identifier (UUID) that identifies a COM component. Each COM component has its CLSID in the Windows registry so that it can be loaded by other applications.

class restrictions
A general term sometimes used for access control by IP address filtering and hostname filtering.

client
On a local area network or the Internet, a computer that accesses shared network resources provided by another computer, called a server. Also, an application or process that requests a service from some process or component. A client facilitates a connection to server computers, and manages and presents information retrieved from those sources. In a client/server environment, the workstation is usually the client computer. When referring to COM objects, a program that accesses or uses a service provided by another component.

client tier
In the three-tier Web application model, the application or process that requests services from the middle tier, which typically includes a Web server and business processes. See also middle tier; data source tier.

client/server architecture
A model of computing whereby client applications running on a desktop or personal computer access information on remote servers or host computers. The client portion of the application is typically optimized for user interaction, whereas the server portion provides centralized, multi-user functionality.

CLSID
See class ID.

clustering
Connecting two or more computers together for the purpose of sharing resources and request load. Each member computer of a cluster is called a node. The nodes in a cluster may either have their own storage devices or share a common device. Typically, clustering will involve support for load balancing, fault tolerance, and fail-over. See also load balancing; node; fault tolerance; failover.

codepage
A codepage is used by the system to encode and interpret string characters. Codepage formats are not the same for each language. Some languages such as Japanese and Hindi have multi-byte characters while others like English and German only need one byte to represent each character. Each codepage is represented by a unique integer. In IIS, the default codepage is the same as CP_ACP. IIS supports Web files saved in UTF-8 format or ANSI format. See also CP_ACP, UTF-8.

colocation
Installing and maintaining a computer at an Internet Service Provider (ISP) that belongs to another company or group. For example, a company might colocate one of their servers at an ISP to save costs, or to make large-scale upgrades easier.

COM
See Component Object Model.

commit
The phase in a transaction when all interactions are finalized and the persistent state of the underlying database is changed.

Common Gateway Interface (CGI)
A server-side interface for initiating software services. The specification that defines communications between information services (such as an HTTP service) and resources on the server's host computer, such as databases and other programs. For example, when a user submits a form through a Web browser, the HTTP service executes a program (often called a CGI script) and passes the user's input information to that program through CGI. The program then returns information to the service through CGI. Any software can be a CGI program if it handles input and output according to the CGI standard. CGI applications always run out-of-process. See also server.

Common Gateway Interface (CGI) bin directory
The directory on a server where CGI script programs are stored. Commonly called CGI-bin or CGI-scripts.

Common Gateway Interface (CGI) script
A program that allows a server to communicate with users on the Internet. For example, when a user enters information in a form on a Web page, a CGI script interprets the information and communicates it to a database program on the server.

Common Object Request Broker Architecture (CORBA)
A specification developed by the Object Management Group in 1992 in which pieces of programs (objects) communicate with other objects in other programs, even if the two programs are written in different programming languages and are running on different platforms. A program makes its request for objects through an object request broker, or ORB, and thus does not need to know the structure of the program from where the object comes. CORBA is designed to work in object-oriented environments.

communications protocol
A set of rules or standards designed to enable computers to connect with one another and to exchange information with as few errors as possible. Some communications protocols contain other protocols, such as hardware protocols and file transfer protocols. Examples include Hypertext Transfer Protocol, Transmission Control Protocol/Internet Protocol (TCP/IP), and Systems Network Architecture (SNA).

compile time
The time during which a program is translated from source language into machine language.

Component Object Model
The object-oriented programming model that defines how objects interact within a single application or between applications. In COM, client software accesses an object through a pointer to an interface-a related set of functions called methods-on the object.

Component Object Model (COM) component
A binary file containing code for one or more class factories, COM classes, registry-entry mechanisms, loading code, and so on. See also Component Object Model; distributed Component Object Model.

concurrency
The appearance of simultaneous execution of processes or transactions by interleaving the execution of multiple pieces of work.

connected user
A user who is currently accessing one of the services of a Web server.

connection pooling
A performance optimization based on using collections of pre-allocated resources, such as objects or database connections. Pooling results in more efficient resource allocation.

content type
The type of file (such as text, graphic, or sound), usually indicated by the file name extension (such as .txt, .gif, or .wav, respectively).

control
In a graphical user interface (GUI), an object on the screen that can be manipulated by a user to perform an action. Perhaps the most common controls are buttons that a user can click to select an option, and scroll bars that a user employs to move through a document or position text in a window.

cookies
A means by which, under the HTTP protocol, a server or a script can maintain information on the client computer. Cookies are small text files which are stored in the user's browser by the Web server. Cookies contain information about the user such as an identification number, a password, how a user shopped on a Web site, or how many times the user visited that site. A Web site can access cookie information whenever the user connects to the server.

CORBA
See Common Object Request Broker Architecture.

counters
See Counters Component (a simple COM object ships with IIS) or Performance Counters (used to measure system performance).

Counters Component
An installable component of IIS that allows you to create, store, increment, or retrieve any number of individual custom counters. Not to be confused with the Performance Counters installed with Windows to monitor system performance.

CP_ACP
The system ANSI CodePage. There is also a system OEM CodePage, CP_OEMCP. See also codepage.

crawler
See spider.

CryptoAPI
See Microsoft Cryptographic API.

Cryptographic Service Provider
The Microsoft CryptoAPI provides a set of functions that allow applications to encrypt or digitally sign data in a flexible manner using certificates. Cryptographic operations (encryption) are performed by independent modules known as cryptographic service providers (CSPs). When you create a certificate for your server, you can select a Microsoft CSP or a third-party CSP if you have one installed. See Microsoft Cryptographic API, encryption.

cryptography
A field science involving the transmission of information in an encoded form so that only an intended recipient can decode the information and reveal its meaning. Encoded information is commonly said to be encrypted.

CSP
See Cryptographic Service Provider.

cursor
An onscreen indicator, such as a blinking underline or rectangle, that marks the place at which a keystroke will appear when typed. In applications and operating systems that use a mouse, the arrow or other onscreen icon that moves with movements of the mouse. Also, a piece of software that returns rows of data to the application. A cursor on a resultset indicates the current position in the resultset.

cycle
In logging, to close an existing log file and start a new one.

# D

daemon
A networking program that performs a housekeeping or maintenance utility function without being called by the user. A daemon sits in the background and is activated only when needed, for example, to correct an error from which another program cannot recover.

Data Encryption Standard (DES)
A specification for encryption of computer data developed by IBM and adopted by the U.S. government as a standard in 1976. DES uses a 56-bit key to protect against password discovery and playback.

datagram
A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between the source and destination computer and the transporting network. See also frame; packet.

data provider
Software that implements Object Linking and Embedding Database (OLE DB) methods and interfaces.

data source
The name that applications use to request a connection to an Open Database Connectivity (ODBC) data source. It specifies the computer name and (optionally) database that the data source name (DSN) maps to. A system data source is a data source that is available to anyone using the computer. Data sources that will be used with a Web server need to be system data sources.

Data Source Name (DSN)
The logical name used by Open Database Connectivity (ODBC) to refer to the drive and other information required to access data. The name is used by Internet Information Services for a connection to an ODBC data source, such as a SQL Server database.

data source tier
A logical layer that represents a computer running a Database Management System (DBMS), such as a SQL Server database. See also client tier; middle tier.

DAV
See Distributed Authoring and Versioning.

DCOM
See distributed COM.

deadlock
In operating systems or databases, a situation in which two or more processes are prevented from continuing while each waits for resources to be freed by the continuation of the other.

debugger
A software tool used to detect the source of program or script errors, by performing step-by-step execution of application code and viewing the content of code variables.

default document
Sometimes called a default home page. The file sent by a Web server when it receives a request for a URL that does not specify a file name. This document can be generated automatically by the server, or it can be a custom file placed in that directory by the administrator.

default gateway
In TCP/IP, the intermediate network device on the local network that has knowledge of the network IDs of the other networks in the Internet, so it can forward the packets to other gateways until they are delivered to the one connected to the specified destination.

DES
See Data Encryption Standard.

design time
The time during which a user builds an application in the development environment by adding controls, setting control or form properties, and so on. In contrast, during run time, a user interacts with the application.

Design-time ActiveX Controls
Visual authoring components that help a developer construct dynamic Web applications by automatically generating standard HTML and scripting code. They are analogous to wizards. Design-time ActiveX Controls exist at design time, and not at run time.

developer isolation
A feature of some software that provides a way for an application developer to create and test scripts without a connecting to a Web server.

DHCP
See Dynamic Host Configuration Protocol.

DHTML
See Dynamic HTML.

dial-up
Of, pertaining to, or being a connection that uses the public switched telephone network rather than a dedicated circuit or some other type of private network. Also called a slow link.

Dial-up Networking
A component of the Windows operating system that makes it possible for users to connect to remote networks such as the Internet or a private network.

Digest authentication
An authentication method that sends user name and password information over the network as a hash value. See also authentication; hash value; hash value comparison.

digital signature
The part of a digital certificate that contains an encryption key that uniquely identifies the holder of the certificate. See also certificate, client; key pair.

directive
An instruction to the Active Server Pages (ASP) script engine that specifies properties, such as script language, for the selection of a script.

directory browsing
A feature that automatically provides a default Web page of available directories and files to browsers that submit a URL that does not specify a particular file.

directory replication
The copying of a master set of directories from a server (called an export server) to specified servers or workstations (called import computers) in the same or other domains. Replication simplifies the task of maintaining identical sets of directories and files on multiple computers, because only a single master copy of the data must be maintained. Files are replicated when they are added to an exported directory, and every time a change is saved to the file.

directory service
Middleware that locates the correct and full network address from a partial name or address typed into a dialog box. See also middleware.

disconnected recordset
A recordset in a client cache that no longer has a live connection to the server. If something must be done with the original data source, such as updating data, the connection will need to be re-established.

discovery mechanism
A way of finding other servers on the network.

Web Distributed Authoring and Versioning (WebDAV)
An extension to the HTTP 1.1 standard that facilitates access to files and directories through an HTTP connection. Remote authors can add, search, delete, or change directories and documents and their properties.

distributed COM
A wire protocol that enables software components to communicate directly over a network.

Distributed interNet Application Architecture (DNA)
Microsoft's architecture for Web applications.

distributed processing
A form of information processing in which work is performed by separate computers linked through a communications network. Distributed processing is usually categorized as either plain distributed processing or true distributed processing. Plain distributed processing shares the workload among computers that can communicate with one another. True distributed processing has separate computers perform different tasks in such a way that their combined work can contribute to a larger goal. The latter type of processing requires a highly structured environment that allows hardware and software to communicate, share resources, and exchange information freely.

DLL
See dynamic-link library.

DNS
See Domain Name System.

domain
In Windows, a collection of computers that share a common domain database and security policy. Each domain has a unique name. See also domain, Internet.

domain controller
For a Windows Server domain, the server that authenticates domain logons and maintains the security policy and the master database for a domain.

domain, Internet
The highest subdivision of a domain name in a network address, which identifies the type of entity owning the address (for example, .com for commercial users or .edu for educational institutions) or the geographical location of the address (for example, .fr for France or .sg for Singapore). The domain is the last part of the address (for example, www.microsoft.com).

domain name
An address of a network connection that identifies the owner of that address in a hierarchical format. For example, www.whitehouse.gov identifies the Web server at the White House, which is a government agency. See also Domain Name System.

Domain Name System (DNS)
The system by which hosts on the Internet have domain name addresses (such as microsoft.com) and IP addresses (such as 172.21.13.45). The domain name address is used by human users and is automatically translated into the numerical IP address, which is used by the packet-routing software. DNS is also the acronym for Domain Name Service, the Internet utility that implements the Domain Name System. DNS servers, also called name servers, maintain databases containing the addresses and are accessed transparently by the user.

Domain Name System (DNS) reverse lookup
Finding the IP address that corresponds to a domain name.

Domain Name System (DNS) spoofing
Assuming the DNS name of another system by either corrupting a name-service cache, or by compromising a domain-name server for a valid domain.

download
In communications, the process of transferring a copy of a file from a remote computer to the requesting computer by means of a modem or network.

DSN
See Data Source Name.

DWORD
The Win32 API designation for a 32-bit integer.

dynamic binding
Binding (converting symbolic addresses in the program to storage-related addresses) that occurs during program execution. The term often refers to object-oriented applications that determine, during run time, which software routines to call for particular data objects. Also called late binding.

Dynamic Host Configuration Protocol (DHCP)
A TCP/IP protocol that enables a network connected to the Internet to assign a temporary IP address to a host automatically when the host connects to the network.

dynamic HTML (DHTML)
A set of innovative features in Internet Explorer version 4.0 and later that can be used to create HTML documents that dynamically change their content and interact with the user. By using DHTML, authors can provide special effects on a Web page without relying on server-side programs.

dynamic-link library (DLL)
A feature of the Microsoft Windows family of operating systems that supports executable routines-usually serving a specific function or set of functions-to be stored separately as files with the file extension name .dll, and to be loaded only when called by the program that needs them. This saves memory during program execution and enables code reusability.

dynamic page
An HTML document that contains animated GIFs, Java applets, ActiveX Controls, or DHTML. Also, a Web page created automatically based on information provided by the user, or generated "on the fly" with ASP.

# E

early binding
See static binding.

e-commerce
Electronic commerce. The process of buying and selling over the Web-often based on software products such as Microsoft Commerce Server.

e-mail
A system whereby a computer user can exchange messages with other computer users (or groups of users) through a communications network. E-mail is one of the most popular uses of the Internet.

encapsulate
To treat a collection of structured information as a whole without affecting or taking notice of its internal structure. In communications, a message or packet constructed according to a protocol such as a TCP/IP packet, may be taken with its formatting data as an undifferentiated stream of bits that is then broken up and packaged according to a lower-level protocol (for example, as ATM packets) to be sent over a particular network; at the destination, the lower-level packets are assembled, re-creating the message as formatted for the encapsulated protocol.

encryption
A way of making data indecipherable to protect it from unauthorized viewing or use, especially during network transmission or when it is stored on a transportable magnetic medium while it is being sent from computer to computer. Encryption can be either symmetric or asymmetric. Symmetric encryption involves the use of the same key to both encrypt and decode the data. Asymmetric encryption uses one key to encrypt and another to decode. See also key pair, Cryptographic Service Provider.

Ethernet
A 10-Mb/s standard for local area networks (LANs) initially developed by Xerox and later refined by Digital, Intel, and Xerox (DIX). All hosts are connected to a coaxial cable where they contend for network access using a CSMA/CD paradigm.

event
Any action, often generated by a user or an ActiveX control, to which a program might respond. Typical events include pressing a keyboard key, choosing a button by using a mouse click, and other mouse actions. Programmers write code to respond to these actions.

event method
A procedure that is invoked only by a particular event, such as On_Click.

exception
In programming, a problem or change in conditions that causes the microprocessor to stop what it is doing and handle the situation in a separate routine. An exception is similar to an interrupt; both refer the microprocessor to a separate set of instructions.

executable program
A program, or collection of programs, forms, data, menus, and other files, that can be run.

expires header
An expiration date or time for a file sent by a server; the expiration information is used by proxy servers and browser caches.

extended partition
Created from free space on a hard disk, an extended partition can be subpartitioned into zero or more logical drives. Only one of the four partitions allowed per physical disk can be an extended partition, and no primary partition needs to be present to create an extended partition. See also logical drive.

eXtensible Markup Language (XML)
A data format for structured document interchange on the Web. It is called the "extensible markup language" because it is not a fixed format like HTML. XML is designed to enable the use of SGML on the World Wide Web. XML is not a single markup language: It is a metalanguage that allows an author to design a markup language. A regular markup language defines a way to describe information in a certain class of documents (for example, HTML). With XML, authors can define their own customized markup language for many classes of documents.

eXtensible Stylesheet Language (XSL)
A stylesheet mechanism that can be used to specify how to transform XML documents into displayable structures. Although XSL defines a grammar of advanced formatting characteristics, it also can be used to generate displayable HTML, or other well-formed markup languages.

extension control block
A data structure created and used by IIS to communicate with an ISAPI extension.

extranet
An extension of a corporate intranet using World Wide Web technology to facilitate communication with the corporation's suppliers and customers. An extranet allows customers and suppliers to gain limited access to a company's intranet in order to enhance the speed of communications and the efficiency of business relationships.

# F

failback
When the failed server node is fully restored to action.

failover
When one individual computer fails, another automatically takes over its request load. The transition is invisible to the user.

FAQ
See Frequently Asked Questions.

fat server
In a client/server architecture, a server computer that performs most of the processing, with little or none performed by the client.

fault tolerance
The ability of a computer or an operating system to respond to a catastrophic event or fault, such as a power outage or a hardware failure, in a way that ensures that no data is lost or corrupted. This can be accomplished with a battery-backed power supply, backup hardware, provisions in the operating system, or any combination of these. In a fault-tolerant network, the system has the ability either to continue the system's operation without loss of data; or to shut the system down and restart it, recovering all processing that was in progress when the fault occurred. See also replication; failover.

file allocation table (FAT) file system
The system used by MS-DOS to organize and manage files. The FAT is a data structure that MS-DOS creates on the disk when the disk is formatted. When MS-DOS stores a file on a formatted disk, the operating system places information about the stored file in the FAT so that MS-DOS can retrieve the file later when requested. The FAT is the only file system MS-DOS can use. See also NTFS.

file name extension mapping
Connecting all files with a certain file name extension to a program. For example, by a default setting in Windows Explorer, all .txt files are associated with Notepad.

file space
A term sometimes used for the file-directory tree of a server.

File Transfer Protocol (FTP)
The protocol used for copying files to and from remote computer systems on a network using Transmission Control Protocol/Internet Protocol (TCP/IP), such as the Internet. This protocol also allows users to use FTP commands to work with files, such as listing files and directories on the remote system.

filter
In IIS, a feature of ISAPI that allows pre-processing of requests and post-processing of responses, permitting site-specific handling of HTTP requests and responses.

filtering, host name
Allowing or denying access based on the host name from which the browser is attempting access.

filtering, IP address
Allowing or denying access based on the IP address from which the browser is attempting access.

finger
An Internet utility that enables a user to obtain information on other users who may be at other sites (if those sites permit access by finger). Given an e-mail address, finger returns the user's full name, an indication of whether or not the user is currently logged on, and any information other users have chosen to supply as a profile. Given a first or last name, finger returns the logon names of users whose first names match. It can also show the last time the user logged on, idle time, terminal line, and terminal location (where applicable), and even project files left by the user.

firewall
A security system intended to protect an organization's network against external threats, such as intruders, coming from another network such as the Internet. A firewall prevents computers in the organization's network from communicating directly with computers external to the network and vice versa. Instead, all communication is routed through a proxy server outside of the organization's network, and the proxy server decides whether it is safe to let a particular message or file pass through. See also proxy server.

footer
In Web publishing, a short addition to every Web page sent out by the server. See server-side include.

form
In Web publishing, a Web page or portion of a Web page that is filled out by the user and sent back to the server for processing.

Fortezza
The U.S. government security standard that satisfies the Defense Messaging System security architecture with a cryptographic mechanism that provides message confidentiality, integrity, authentication, and access control to messages, components, and systems. These features can be implemented both with server and browser software and with Personal Computer Memory Card International Association (PCMCIA) hardware. A Fortezza card is a type of PCMCIA card, similar to those used in notebook computers and other small devices. This card can store a private key used by the server to authenticate users. See also Crypto Service Provider.

frame
In asynchonous serial communications, a unit of transmission that is sometimes measured in elapsed time. It begins with the start bit that precedes a character and ends with the last stop bit that follows the character. In synchronous communications, a package of information transmitted as a single unit. Every frame follows the same basic organization and contains control information, such as synchronizing characters, station address, and an error-checking value, as well as a variable amount of data. See also datagram; encapsulate; packet.

Frequently Asked Questions (FAQ)
Usually a document containing questions and answers that address basic questions. A visitor can find an FAQ on many Web sites. An FAQ serves to introduce a visitor to the topic or subject of the Web site and to offer general guidelines about how to best use the site.

friendly name
Also called a host name. A name that substitutes for an IP address, for example, www.microsoft.com instead of 172.16.255.255.

FrontPage Server Extensions
A group of files installed on an HTTP service to give that service the ability to provide special Microsoft FrontPage functionality. With FrontPage Server Extensions, administrators can view and manage a Web site in a graphical interface. Also, authors can create, edit, and post Web pages to IIS remotely.

FTP
See File Transfer Protocol.

# G

gateway
A device that connects networks using different communications protocols so that information can be passed from one to the other. A gateway both transfers information and converts it to a form compatible with the protocols used by the receiving network.

GIF
See Graphics Interchange Format.

Global.asa
A file that stores information about an IIS application such as initialization in structures, and objects that have been given application scope.

globally unique identifier (GUID)
In COM, a 16-byte code that identifies an interface to an object across all computers and networks. Such an identifier is unique because it contains a time stamp and a code based on the network address hard-wired on the host computer's LAN interface card. These identifiers are generated by a utility program.

Gopher
An early Internet protocol and software program designed to search for, retrieve, and display text documents from remote computers or sites.

graphical user interface (GUI)
A type of environment that represents programs, files, and options by means of icons, menus, and dialog boxes on the screen. The user can select and activate these options by pointing and clicking with a mouse or, often, with a keyboard.

Graphics Interchange Format (GIF)
A computer graphics file format developed in the mid-1980s by CompuServe for use in photo-quality graphic image display on computer screens. Now commonly used on the Internet.

GUI
See graphical user interface.

GUID
See globally unique identifier.

# H

handshake
A series of signals acknowledging that communication or the transfer of information can take place between computers or other devices. A hardware handshake is an exchange of signals over specific wires (other than the data wires), in which each device indicates its readiness to send or receive data. A software handshake consists of signals transmitted over the same wires used to transfer data, as in modem-to-modem communications over telephone lines.

hash value
A small amount of binary data, typically around 160 bits, derived from a message by using a hashing algorithm. The hashing procedure is one-way. There is no feasible way of deriving the original message, or even any of its properties, from the hash value, even given the hashing algorithm. The same message will always produce the same hash value when passed through the same hashing algorithm. Messages differing by even one character can produce very different hash values.

hash value comparison
When a client or server receives a hash value as part of an authentication scheme it will use a commonly known key value, such as a password, to create a hash value and compare the generated hash value with the one it received. If they are identical, authentication is accepted. See also replication.

heap (Windows heap)
An area of working memory provided by Windows that applications can use to store data.

hit
A successful retrieval of data from a cache rather than from the slower hard disk or RAM; a successful retrieval of a record matching a query in a database; or the retrieval of a document, such as a home page, from a Web site. See also usage data.

home directory
The root directory for a Web site, where the content files are stored. Also called a document root or Web root. In Internet Information Services, the home directory and all its subdirectories are available to users by default. Also the root directory for an IIS service. Typically the home directory for a site contains the home page. See also home page.

home page
The initial page of information for a collection of pages, a Web site or section of a Web site. See also default document.

host
The main computer in a system of computers or terminals connected by communications links.

host name
The name of a specific server on a specific network within the Internet, leftmost in the complete host specifications. For example, www.microsoft.com indicates the server called "www" within the network at the Microsoft Corporation.

HTML
See Hypertext Markup Language.

HTTP
See Hypertext Transfer Protocol.

HTTPD
HTTP Daemon; a Web server.

HTTP header
An informational listing at the top of an HTTP request or response.

hyperlink
A connection between an element in a hyptertext document, such as a word, phrase, symbol, or image, and a different element in the document, another hypertext document, a file, or a script. The user activates the link by clicking on the linked element, which is usually underlined or in a color different from the rest of the document. Hyperlinks are indicated in a hypertext document by the use of tags in markup languages such as SGML and HTML. These tags are generally not visible to the user. Also called hot links and hypertext links.

hypertext
Text linked together in a complex, nonsequential web of associations in which the user can browse through related topics. The term hypertext was coined in 1965 to describe documents presented by a computer that express the nonlinear structure of ideas as opposed to the linear format of books, film, and speech.

Hypertext Markup Language (HTML)
A simple markup language used to create hypertext documents that are portable from one platform to another. HTML files are simple ASCII text files with codes embedded (indicated by markup tags) to indicate formatting and hypertext links. The formatting language used for documents on the World Wide Web. See also Dynamic HTML; eXtensible Markup Language; Standard Generalized Markup Language.

Hypertext Transfer Protocol (HTTP)
The client/server protocol used to access information on the World Wide Web.

# I

ICMP
See Internet Control Message Protocol.

identities, multiple
A term sometimes used for multiple Web sites hosted on one computer; also called virtual servers.

IETF
See Internet Engineering Task Force.

IIS Admin Base Object
A DCOM object that implements the IMSAdminBase interface, using methods that enable a Web application to manipulate IIS configuration keys and data in the memory-resident metabase.

IIS Admin Objects
A set of methods provided by IIS that allow applications to access and modify configuration settings in the metabase.

image map
An image that contains more than one hyperlink on a Web page. Clicking on different parts of the image links the user to other resources on another part of the Web page, a different Web page, or a file. Often an image map, which can be a photograph, drawing, or a composite of several different drawings or photographs, is used as a map to the resources found on a particular Web site. Image maps are created with CGI scripts. Image maps can be server-side or client-side. Server-side image maps map each URL on the server. Client-side image maps, on the other hand, do not require mediating server-side scripts because the URL mapping is contained in an HTML file. See also Common Gateway Interface (CGI) script; hyperlink.

index file
See default document.

inheritance
Generally, the ability of a newly-created object to automatically have, or inherit, properties of an existing object. For example, a newly created child directory can inherit the access-control settings of the parent directory.

in-process component
A component that runs in a client's process space. This component is typically a dynamic-link library (DLL).

instance
An object of a particular component class. Each instance has its own private data elements or member variables. Component instance is synonymous with object.

instantiate
To create an instance of an object.

Integrated Services Digital Network (ISDN)
Combines voice and digital network services in a single medium, making it possible to offer telephone customers digital data service and voice connection through a single "wire." A dial-up ISDN line can offer speeds of up to 128,000 bps. A type of phone line used to enhance wide area network (WAN) speeds, an ISDN line can transmit at speeds of 64 kilobits or 128 kilobits per second. An ISDN line must be installed by the phone company at both the server site and the remote site.

integrated Windows authentication
A method of authentication in which a server verifies user account information by means of a cryptographic exchange; actual passwords are never transmitted. Formerly known as NTLM and Challenge/Response authentication.

interface
A group of logically related operations or methods that provides access to a component object.

internal Web
An intranet; also sometimes called an internal network, private network, local area network (LAN), or wide area network (WAN). See also intranet; local area network; wide area network.

International Organization for Standardization (ISO)
A voluntary, nontreaty organization founded in 1946 which is responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of the 89 member countries/regions, including ANSI for the U.S. See also American National Standards Institute.

International Organization for Standardization Open Systems Interconnection model (ISO/OSI model) A layered architecture (plan) that standardizes levels of service and types of interaction for computers exchanging information through a communications network. The ISO/OSI model separates computer-to-computer communications into seven layers, or levels, each building upon the standards contained in the levels below it. The lowest of the seven layers deals solely with hardware links; the highest deals with software interactions at the application-program level.

Internet
Abbreviation for internetwork. A set of dissimilar computer networks joined together by means of gateways that handle data transfer and the conversion of messages from the sending network to the protocols used by the receiving networks. These networks and gateways use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols. Originally part of the Defense Advanced Research Projects Agency (DARPA), operated by the U.S. Department of Defense.

Internet Control Message Protocol (ICMP)
An extension to Internet Protocol (IP), ICMP allows for the generation of error messages, test packets, and informational messages related to IP. See also Packet INternet Groper (PING).

Internet Engineering Task Force (IETF)
A protocol engineering and development organization focused on the Internet. The IETF is a large, open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is now under the auspices of the Internet Society, a non-governmental international organization for global cooperation and coordination for the Internet and its internetworking technologies and applications. For more information, see the Internet Society Web site.

Internet Network Information Center (InterNIC)
Former coordinator for DNS registration of names in the .com, .net, .org, .edu, .gov, and .mil top-level domains. InterNIC has been replaced by Network Solutions. For more information, see the Network Solutions Web site.

Internet Protocol (IP)
The part of Transmission Control Protocol/Internet Protocol (TCP/IP) that routes messages from one Internet location to another. IP is responsible for addressing and sending Transmission Control Protocol (TCP) packets over the network. IP provides a best-effort, connectionless delivery system that does not guarantee that packets arrive at their destination or that they are received in the sequence in which they were sent. See also packet.

Internet Protocol address (IP address)
A unique address that identifies a host on a network. It identifies a computer as a 32-bit address that is unique across a Transmission Control Protocol/Internet Protocol (TCP/IP) network. An IP address is usually represented in dotted-decimal notation, which depicts each octet (eight bits, or one byte) of an IP address as its decimal value and separates each octet with a period. For example: 172.16.255.255.

Internet Server Application Program Interface (ISAPI)
An application program interface that resides on a server computer for initiating software services tuned for the Microsoft Windows operating system. It is an API for developing extensions to IIS and other HTTP services that support the ISAPI interface. See also Application Programming Interface; Common Gateway Interface.

Internet service
Any protocol for transferring information over the Internet, except HTTP. The protocol is the first part of the full URL for a resource. Internet service types include Gopher, telnet, WAIS, NNTP, HTTP, and FTP. See also Hypertext Transfer Protocol; protocol.

Internet service provider (ISP)
Public provider of remote connections to the Internet. A company or educational institution that enables remote users to access the Internet by providing dial-up connections or installing leased lines.

interoperability
The ability of software and hardware on multiple computers from multiple vendors to communicate meaningfully.

intranet
A network designed for information processing within a company or organization. Its uses include such services as document distribution, software distribution, access to databases, and training. An intranet is so called because it usually employs applications associated with the Internet, such as Web pages, Web browsers, FTP sites, e-mail, newsgroups, and mailing lists, in this case accessible only to those within the company or organization.

IP
See Internet Protocol.

ISAPI
See Internet Server Application Programming Interface (ISAPI).

ISDN
See Integrated Services Digital Network.

ISO/OSI model
See International Organization for Standardization Open Systems Interconnection model.

ISP
See Internet service provider.

# J

Java
An object-oriented programming language developed by Sun Microsystems, Inc. Currently, the most widespread use of Java is in programming small applications, or applets, for the World Wide Web.

JavaBeans
An object model being developed by SunSoft that is targeted to interoperate with a variety of other object models, including COM and CORBA. See also Common Object Request Broker Architecture; Component Object Model.

Java Database Connectivity (JDBC)
Data access interfaces based on ODBC for use with the Java language.

JavaScript
A scripting language developed by Netscape Communications that is syntactically similar to Java. JavaScript, however, is not a true object-oriented language, and it is limited in performance compared with Java because it is not compiled. A JavaScript-client Web browser is necessary to run JavaScript code. Now an open standard known as the ECMA 262 language specification. See also JScript.

Java virtual machine
Software on a computer that runs Java applets.

JDBC
See Java Database Connectivity.

JIT
See just-in-time activation.

Joint Photographic Experts Group (JPEG)
An ISO/ITO standard for storing images in compressed form using a discrete cosine transform. JPEG trades off compression against loss; it can achieve a compression ratio of 100:1 with significant loss and up to 20:1 with little noticeable loss.

JPEG
See Joint Photographic Experts Group.

JScript
The Microsoft open implementation of JavaScript. JScript complies with the ECMA 262 language specification.

just-in-time activation (JIT)
The ability of a COM object to be activated only as needed for executing requests from its client. Objects can be deactivated even while clients hold references to them, allowing otherwise idle server resources to be used more productively.

# K

Keep-Alive connection
An HTTP connection that is not closed after an exchange is completed.

Kerberos protocol
The basis of Windows security, for both internal and intranet logon. The Kerberos protocol provides for the secure use of distributed software components. See also cryptography; encryption.

key
A node in the Windows registry or IIS metabase. A key can contain subkeys and value entries. For example: Environment is a key of HKEY_CURRENT_USER.

key pair
The combination of private and public encryption keys that provides verification of the source of data sent across a network. See also certificate, client; digital signature; session key.

keyword
In search-engine technology, a significant word, which is used for content indexing; see also noise word. In programming, a word reserved for a command or other program instruction.

keyword index
A file of significant words appearing in documents; used for keyword searches.

# L

LAN
See local area network.

late binding
See dynamic binding.

LCID
See Locale Identifier.

LDAP
See Lightweight Directory Access Protocol.

Lightweight Directory Access Protocol (LDAP)
A network protocol designed to work on Transmission Control Protocol/Internet Protocol (TCP/IP) stacks to extract information from a hierarchical directory. This gives users a single tool to search through data to find a particular piece of information, such as a user name, e-mail address, security certificate, or other contact information.

link
See hyperlink.

load balancing
When a server cluster shares the information requests equally over all of its active nodes. This can be done either statically, by tying clients directly to different back-end servers, or dynamically by having each client tied to a different back-end server controlled by software or a hardware device. The Network Load Balancing feature of Windows 2000 Advanced Server provides load balancing for HTTP services.

local area network (LAN)
A group of computers and other devices intended to serve an area of only a few square kilometers or less and connected by a communications link that enables any device to interact with any other on the network. Because the network is known to cover only a small area, optimizations can be made in the network signal protocols that permit data rates of up to 100 Mbps. See also Ethernet; token ring; wide area network.

local group
A group that can be granted permissions and rights only for its own workstation. However, it can contain user accounts from its own computer and (if the workstation participates in a domain) user accounts and global groups both from its own domain and from trusted domains.

Locale Identifier (LCID)
The locale refers to the formatting style of dates, times, currencies and other values, which is different for each geographical location. Each locale is represented by a unique integer. In IIS, the default LCID is the same as the system locale. See also LOCALE_SYSTEM_DEFAULT.

LOCALE_SYSTEM_DEFAULT
The default system locale. There is also a default user locale. See Locale Identifier.

localhost
A placeholder for the name of the computer on which a program is running; localhost uses the reserved loopback IP address 127.0.0.1.

log file
The file in which logging records are stored. This file can be either a text file or a database file.

logging
Storing information about events that occurred on a firewall or network.

logical drive
A subpartition of an extended partition on a hard disk. See also extended partition.

# M

main thread
A single thread used to run all objects of components marked as "Single-threaded." See also Apartment thread.

Mail or Messaging Applications Programming Interface (MAPI)
An open and comprehensive messaging interface used by developers to create messaging and workgroup applications-such as e-mail, scheduling, calendaring, and document management. In a distributed client/server environment, MAPI provides enterprise messaging services within Windows Open Services Architecture (WOSA).

Management Information Base (MIB)
Information about aspects of a network that can be managed by using the Simple Network Management Protocol (SNMP). This information is formatted in MIB files that are provided for each service that can be monitored. Most third-party monitors (clients) use SNMP and MIB files to monitor Web, FTP, and other Windows services. Using the SNMP protocol, a developer or system administrator can write their own custom monitoring applications.

MAPI
See Mail or Messaging Applications Programming Interface.

marshaling
The process of packaging and sending interface method parameters across thread or process boundaries.

master properties
In IIS, properties that are set at the computer level that become default settings for all Web or FTP sites on that computer. See also inheritance.

MDAC
See Microsoft Data Access Components.

Message Digest 5 (MD5)
An encryption method used on the Internet.

message passing
A method for processes running in parallel to interact with one another.

Message Queuing
A server technology that developers can use to build large-scale distributed systems with reliable communications between applications that can continue to operate even when networked systems are unavailable.

meta-authoring environment
A term sometimes used for the process of both authoring Web pages and setting up a Web site.

metabase
A structure for storing IIS configuration settings; the metabase performs some of the same functions as the system registry, but uses less disk space.

metadata
Data used to describe other data. For example, Indexing Service must maintain data that describes the data in the content index.

method
A procedure (function) that acts on an object.

MIB
See Management Information Base.

Microsoft Cryptographic API
An application programming interface providing services for authentication, encoding, and encryption in Win32-based applications. See also Cryptographic Service Provider, encryption.

Microsoft Data Access Components (MDAC)
Consists of ActiveX Data Objects (ADO), the Remote Data Service (RDS), Microsoft OLE DB Provider for ODBC, Open Database Connectivity (ODBC), ODBC drivers for Microsoft SQL Server, Microsoft Access and other desktop databases, as well as Oracle databases.

Microsoft Visual Basic (VB)
A high-level, visual-programming version of Basic. Visual Basic was designed for building Windows-based applications.

Microsoft Visual Basic for Applications (VBA)
The development environment and language found in Visual Basic that can be hosted by applications.

Microsoft Visual Basic Scripting Edition (VBScript)
A subset of the Microsoft Visual Basic language, VBScript is implemented as a fast, portable, lightweight interpreter for use in World Wide Web browsers and other applications that use ActiveX Controls and Java applets.

middle tier
Also known as application server tier. The logical layer between a user interface or Web client and the database. This is typically where the Web server resides, and where business objects are instantiated. See also client tier; data source tier.

middleware
The network-aware system software, layered between an application, the operating system, and the network transport layers, whose purpose is to facilitate some aspect of cooperative processing. Examples of middleware include directory services, message-passing mechanisms, distributed transaction processing (TP) monitors, object request brokers, remote procedure call (RPC) services, and database gateways.

mirror set
A fully redundant or shadow copy of data. Mirror sets provide an identical twin for a selected disk; all data written to the primary disk is also written to the shadow or mirror disk. The user can then have instant access to another disk with a redundant copy of the information on the failed disk. Mirror sets provide fault tolerance. See also fault tolerance.

modem
Modulator/demodulator. A communications device that enables a computer to transmit information over a standard telephone line.

MSMQ
See Message Queuing.

multihomed host
A host which has a connection to more than one physical network. The host may send and receive data over any of the links but will not route traffic for other nodes. See also host; router.

Multipurpose Internet Mail Extensions mapping (MIME mapping)
A way of configuring browsers to view files that are in multiple formats. An extension of the Internet mail protocol that enables sending 8-bit based e-mail messages, which are used to support extended character sets, voice mail, facsimile images, and so on.

multithreading
Running several processes in rapid sequence within a single program, regardless of which logical method of multitasking is being used by the operating system. Because the user's sense of time is much slower than the processing speed of a computer, multitasking appears to be simultaneous, even though only one task at a time can use a computer processing cycle.

multitier architecture
Also known as three-tier architecture, multitier architecture is a technique for building applications generally split into user, business, and data services tiers. These applications are built of component services that are based on an object model such as COM. See also three-tier architecture.

# N

name resolution
The method of mapping friendly names to IP addresses. See also friendly name.

natural language query
A query to a database system that is composed in a subset of natural language, such as English or Japanese. The query must conform to some restrictive syntax rules in order to be parsed.

Network News Transfer Protocol (NNTP)
The protocol used to distribute network news messages to NNTP servers and to NNTP clients (news readers) on the Internet. NNTP provides for the distribution, inquiry, retrieval, and posting of news articles by using a reliable stream-based transmission of news on the Internet. NNTP is designed so that news articles are stored on a server in a central database, thus users can select specific items to read. Indexing, cross-referencing, and expiration of aged messages are also provided. Defined in RFC 977.

network sniffer
A hardware and software diagnostic tool that can also be used to decipher passwords, which may result in unauthorized access to network accounts. Clear-text passwords are susceptible to network sniffers.

NNTP
See Network News Transfer Protocol.

node
A computer that is attached to a network; also called a host. A node is also a junction of some kind. On a local area network, a node is a device that is connected to the network and is capable of communicating with other network devices.

noise word
An insignificant word, such as the, and, or be which is ignored during indexing; also called an ignored word.

NTFS
A file system designed for use specifically with the Windows operating system. It supports long file names, full security access control, file system recovery, extremely large storage media, and various features for the Windows POSIX subsystem. It also supports object-oriented applications by treating all files as objects with user-defined and system-defined attributes. See also file allocation table (FAT) file system.

# O

object
In object-oriented programming, a variable comprising both routines and data that is treated as a discrete entity. An object is based on a specific model, where a client using an object's services gains access to the object's data through an interface consisting of a set of methods or related functions. The client can then call these methods to perform operations.

object-cache scavenger
The code that periodically scans the cache for objects to be discarded. It deletes from the cache files that have not been used recently and therefore are unlikely to be used again in the near future.

Object Identifiers
Extensible, unique, identification numbers for attributes and classes. Performance counter names have their own OIDs, listed in MIB files, to provide performance monitoring applications with access to the counters. See also SNMP, MIB.

Object Linking and Embedding (OLE)
A set of integration standards to transfer and share information among client applications. A protocol that enables creation of compound documents with embedded links to applications so that a user does not have to switch among applications in order to make revisions. OLE is based on the Component Object Model (COM) and allows for the development of reusable objects that are interoperable across multiple applications. The technology has been broadly used in business, where spreadsheets, word processors, financial packages, and other applications can share and link disparate information across client/server architectures.

Object Linking and Embedding Database (OLE DB)
Data-access interfaces providing consistent access to SQL and non-SQL data sources across the enterprise and the Internet. See also Structured Query Language.

object orientation
Representing the latest approach to accurately model the real world in computer applications, object orientation is an umbrella concept used to describe a suite of technologies that enable software products that are highly modular and reusable. Applications, data, networks, and computing systems are treated as objects that can be mixed and matched flexibly rather than as components of a system with built-in relationships. As a result, an application need not be tied to a specific system or data to a specific application. The four central object-oriented concepts are encapsulation, message passing, inheritance, and late binding.

Object Management Group (OMG)
A vendor alliance formed to define and promote CORBA object specifications.

Object Request Broker (ORB)
In client/server applications, an interface to which the client makes a request for an object. The ORB directs the request to the server containing the object and then returns the resulting values to the client.

octet
Eight contiguous bits, or a byte. The term was created because some computer systems attached to the Internet used a byte with more than eight bits.

ODBC
See Open Database Connectivity.

OID
See Object Identifiers.

OLE
See Object Linking and Embedding.

OLE DB
See Object Linking and Embedding Database.

OMG
See Object Management Group.

Open Database Connectivity (ODBC)
An application programming interface that enables applications to access data from a variety of existing data sources. A standard specification for cross-platform database access.

Open Group, The
The parent company of a number of standards organizations including The Active Group. The Open Group now manages the core ActiveX technology, X/Open, and the Open Software Foundation (OSF).

ORB
See Object Request Broker.

out-of-process component
A COM component that runs in a separate process space from its client.

# P

packet
A transmission unit of fixed maximum size that consists of binary information representing both data and a header containing an ID number, source and destination addresses, and error-control data. A piece of information sent over a network.

Packet INternet Groper (PING)
A command used to verify connections to one or more remote hosts. The ping utility uses the ICMP echo request and echo reply packets to determine whether a particular IP system on a network is functional. The ping utility is useful for diagnosing IP network or router failures. The term is also used as a verb. See also Internet Control Message Protocol; router.

page
See Web page.

parameter
A value passed in a function call.

parity
The quality of sameness or equivalence, in the case of computers usually referring to an error-checking procedure in which the number of ones must always be the same-either even or odd-for each group of bits transmitted without error. If parity is checked on a per-character basis, the method is called vertical redundancy checking, or VRC; if its checked on a block-by-block basis, the method is called longitudinal redundancy checking, or LRC. In typical modem-to-modem communications, parity is one of the parameters that must be agreed upon by sending and receiving parties before transmission can take place. See also fault tolerance; stripe set; stripe sets with parity.

partition
A portion of a physical disk that functions as though it were a physically separate unit.

password authentication
See authentication.

path, physical
A universal naming convention (UNC) directory path. See also path, relative.

path, relative
A UNC directory path with placeholders, or wildcards, at some levels. The term relative path is also sometimes used to mean the physical path that corresponds to a URL. See also Uniform Resource Locator.

path, URL
A term sometimes used for the full URL submitted to the server; a URL path may or may not include a specific file name. See also Uniform Resource Locator.

PDH
See Performance Data Helper.

Perfmon
See Performance Monitor.

Performance Counters
Counters are references that measure the performance of applications, services, or drivers. Counters can be monitored using protocol interfaces such as PDH or SNMP, or by using the Performance Monitor MMC snap-in (Perfmon).

Performance Data Helper
A network monitoring protocol in Windows. Performance monitoring is the process of capturing and analyzing the performance data that applications, services, and drivers provide. The data can be used to determine the cause of system bottlenecks and to fine-tune system and application performance. PDH is an interface for accessing this data. The Windows Performance Monitor (Perfmon) uses PDH. See also Simple Network Management Protocol.

Performance Monitor
An MMC snap-in that shows real-time data and logs from Performance Counters. The data can be used to determine the cause of system bottlenecks and to fine-tune system and application performance. Counters can be added and removed from the display, or configured to log in a certain way. See also Performance Counters, Performance Data Helper.

Perl
Practical Extraction and Report Language. An interpreted language, based on C and several UNIX utilities. Perl has powerful string-handling features for extracting information from text files. Perl can assemble a string and send it to the shell as a command; hence, it is often used for system administration tasks. A program in Perl is known as a script. Perl was devised by Larry Wall at NASA's Jet Propulsion Laboratory. See also script.

PGP
See Pretty Good Privacy.

physical transaction
The actual updating of the data resources that are used to record a logical transaction.

PING
See Packet INternet Groper.

Point-to-Point Protocol (PPP)
A set of industry-standard framing and authentication protocols included with Windows Remote Access Service (RAS) to ensure interoperability with third-party remote access software. PPP negotiates configuration parameters for multiple layers of the OSI (Open Systems Interconnection) model. The Internet standard for serial communications, PPP defines how data packets are exchanged with other Internet-based systems using a modem connection.

Point-to-Point Tunneling Protocol (PPTP)
A specification for virtual private networks in which some nodes of a local area network are connected through the Internet. PPTP is an open industry standard that supports the most prevalent networking protocols-IP, IPX, and Microsoft Networking (NetBEUI). Companies can use PPTP to outsource their remote dial-up needs to an Internet service provider or other carrier to reduce cost and complexity.

policies
Conditions set by the system administrator such as how quickly account passwords expire and how many unsuccessful logon attempts are allowed before a user is locked out. These policies manage accounts to prevent exhaustive or random password attacks.

port number
A number identifying a certain Internet application. For example, the default port number for the WWW service is 80.

PPP
See Point-to-Point Protocol.

PPTP
See Point-to-Point Tunneling Protocol.

Pretty Good Privacy (PGP)
A security application that uses public-key encryption. See also public-key encryption.

process
In Windows, an object consisting of an executable program, a set of virtual memory addresses, and a thread; in UNIX, a synonym for thread. See also thread.

process accounting
A feature of IIS that allows administrators to monitor and log resource consumption of CGI scripts and out-of-process applications.

process isolation
Running an application or component out-of-process. See also out-of-process component.

program file
A file that starts an application or program. A program file has an .exe, .pif, .com, .cmd, or .bat file name extension.

programmatic security
Procedural logic provided by a component to determine if a client is authorized to perform the requested operation.

properties, document
Information about a document and its physical location on a hard disk.

properties, link
Information about an HTML document and the full URL associated with it.

protocol
The method by which computers communicate on the Internet. The most common protocol for the World Wide Web is HTTP. Other Internet protocols include FTP, Gopher, and telnet. The protocol is part of the full URL for a resource.

proxy
A software program that connects a user to a remote destination through an intermediary gateway.

proxy server
A firewall component that manages Internet traffic to and from a local area network and can provide other features, such as document caching and access control. A proxy server can improve performance by caching and directly supplying frequently requested data, such as a popular Web page, and can filter and discard requests that the owner does not consider appropriate, such as requests for unauthorized access to proprietary files. See also firewall.

public-key encryption
An asymmetric scheme that uses a pair of keys for encryption: The public key encrypts data, and a corresponding secret key decrypts it. For digital signatures, the process is reversed: The sender uses the secret key to create a unique electronic number that can be read by anyone possessing the corresponding public key, which verifies that the message is truly from the sender. See also RSA; session key.

# Q

query form
An online form that the user fills out to search for information by keyword or concept; also called a search interface.

query restriction
What to look for in a search; a query restriction narrows the focus of a search. Also called a search expression or search string.

# R

RAID
See Redundant Array of Independent Disks.

RAM
See random access memory.

random access memory (RAM)
Semiconductor-based memory that can be read and written by the central processing unit (CPU) or other hardware devices. The storage locations can be accessed in any order. Note that various types of ROM memory are capable of random access but cannot be written to. The term RAM is generally understood to refer to volatile memory that can be written to as well as read. Information stored in RAM is lost when the user turns off the computer.

RARP
See Reverse Address Resolution Protocol.

RAS
See Remote Access Service.

realm
A term sometimes used for domain, in this case to refer to user domains established for security reasons, not Internet domains. For password-protected files, the name of the protected resource or area on the server. If the user tries to access the protected resource while browsing, the name of the realm usually appears in the dialog box that asks for a user name and password.

redirection
The process of writing to or reading from a file or device different from the one that would normally be the target or the source. Can be used to automatically send a user from an outdated URL to a new one.

Redundant Array of Independent Disks (RAID)
A data storage method in which data, along with information used for error correction, such as parity bits, is distributed among two or more hard disk drives in order to improve performance and reliability. The hard disk array is governed by array management software and a disk controller, which handles the error correction. RAID is generally used on network servers. Several defined levels of RAID offer differing trade-offs among access speed, reliability, and cost. Windows includes three of the RAID levels: Level 0, Level 1, and Level 5.

registry
A central hierarchical database in Windows used to store information necessary to configure the system for one or more users, applications, and hardware devices. The registry contains information that is constantly referenced during operation, such as profiles for each user, the applications installed on the computer; and the types of documents each can create, property sheet settings for folders and application icons, what hardware exists on the system; and which ports are being used.

Remote Access Service (RAS)
A service that allows remote clients running Microsoft Windows to dial-in to a network. See also dial-up.

Remote Data Services
A Web-based technology that brings database connectivity and corporate data publishing capabilities to Internet and intranet applications.

remote procedure call (RPC)
In programming, a call by one program to a second program on a remote system. The second program usually performs a task and returns the results of that task to the first program.

replication
Copying from one server node to another of either content or the configuration metabase, or both. This copying can either be done manually or automatically by using replication software. Replication is a necessary function of clustering to ensure fault tolerance. See also fault tolerance; clustering.

Request for Comments (RFC)
The document series, begun in 1969, which describes the Internet suite of protocols and related experiments. Not all (in fact very few) RFCs describe Internet standards, but all Internet standards are written up as RFCs. The RFC series of documents is unusual in that the proposed protocols are forwarded by the Internet research and development community, acting on their own behalf, as opposed to the formally reviewed and standardized protocols that are promoted by organizations such as ANSI. See also American National Standards Institute.

resource dispenser
A service that provides the synchronization and management of nondurable resources within a process, providing for simple and efficient sharing by COM objects. For example, the ODBC resource dispenser manages pools of database connections. See also Open Database Connectivity.

resource manager
A system service that manages durable data. Server applications use resource managers to maintain the durable state of the application, such as the record of inventory on hand, pending orders, and accounts receivable. The resource managers work in cooperation with the transaction manager to provide the application with a guarantee of atomicity and isolation (using the two-phase commit protocol). Microsoft SQL Server is an example of a resource manager.

Reverse Address Resolution Protocol (RARP)
A TCP/IP protocol for determining the IP address (or logical address) of a node on a local area network connected to the Internet, when only the hardware address (or physical address) is known. Although the acronym RARP refers only to finding the IP address, and Address Resolution Protocol (ARP) technically refers to the opposite procedure, the acronym ARP is commonly used to describe both procedures.

RFC
See Request For Comments.

robot
An automated program such as a search engine, indexing program, or cataloging software, that requests Web pages much faster than human beings can. Other commonly used terms for robot include crawler and spider.

router
An intermediary device on a communications network that expedites message delivery. On a single network linking many computers through a mesh of possible connections, a router receives transmitted messages and forwards them to their correct destinations over the most efficient available route. On an interconnected set of local area networks (LANs) using the same communications protocols, a router serves the somewhat different function of acting as a link between LANs, enabling messages to be sent from one to another.

RPC
See remote procedure call.

RSA
A public-key encryption standard for Internet security. This acronym derives from the last names of the inventors of the technology: Rivest, Shamir, and Adleman.

run time
The time during which a program actually runs. See also design time.

# S

scalability
The capability to use the same software environment on many classes of computers and hardware configurations. Although often associated with an evolution to large systems, larger organizations often have need for the same software service to be provided with good performance to both small and large groups of users.

scope
In programming, the extent to which an identifier, such as a constant, data type, variable, or routine, can be referenced within a program. Scope can be global or local. Scope can also be affected by redefining identifiers, such as by giving the same name to both a global variable and a local variable.

script
A kind of program that consists of a set of instructions for an application or utility program. A script can be embedded in a Web page. See also ActiveX; Common Gateway Interface.

scripting engine
A program that interprets and executes a script. See also script.

search expression
See query restriction.

search interface
See query form.

search string
See query restriction.

Secure Sockets Layer (SSL)
A protocol that supplies secure data communication through data encryption and decryption. SSL uses RSA public-key encryption for specific TCP/IP ports. It is intended for handling commerce payments. An alternative method is Secure-HTTP (S-HTTP), which is used to encrypt specific Web documents rather than the entire session. SSL is a general-purpose encryption standard. SSL can also be used for Web applications requiring a secure link, such as e-commerce applications, or for controlling access to Web-based subscription services.

security log
A log, generated by a firewall or other security device, that lists events that could affect security, such as access attempts or commands, and the information about the users involved.

Selectable Cryptographic Service Provider
See Cryptographic Service Provider.

semaphore
A locking mechanism used inside resource managers or resource dispensers. Semaphores have no symbolic names-only shared and exclusive mode access-no deadlock detection, and no automatic release or commit.

server
A term used for any of the following: a computer on a network that sends files to, or runs applications for, other computers on the network; the software that runs on the server computer and performs the work of serving files or running applications; or, in object-oriented programming, a piece of code that exchanges information with another piece of code upon request.

server certificate
A unique digital identification that forms the basis of a Web server's SSL security features. Server certificates are obtained from a mutually trusted, third-party organization, and provide a way for users to authenticate the identity of a Web site.

server cluster
A group of server computers that are networked together both physically and with software, in order to provide cluster features such as fault tolerance or load balancing. See also fault tolerance; load balancing.

server node
An individual computer in a server cluster.

server process
A process that hosts COM components. A COM component can be loaded into a surrogate server process, either on the client computer (local) or on another computer (remote). It can also be loaded into a client application process (in-process).

server scriptlet
A COM object that is created with Microsoft Server Scriptlet technology.

server-side include
A mechanism for including dynamic text in World Wide Web documents. Server-side includes are special command codes that are recognized and interpreted by the server; their output is placed in the document body before the document is sent to the browser. Server-side includes can be used, for example, to include the date/time stamp in the text of the file.

session key
A digital key that is created by the client, encrypted, and sent to the server. This key is used to encrypt data sent by the client. See also certificate, client; digital signature; key pair.

SGML
See Standard Generalized Markup Language.

shared property
In Component Services, a variable that is available to all objects in the same server process through the Shared Property Manager. The value of the property can be any type that can be represented by a variant.

Simple Mail Transfer Protocol (SMTP)
A TCP/IP protocol for sending messages from one computer to another on a network. This protocol is used on the Internet to route e-mail.

Simple Network Management Protocol (SNMP)
The network management protocol of TCP/IP. In SNMP, agents or clients monitor the activity of various devices on the network and report to the network console workstation. The agents or clients can be hardware as well as software. Control information about each device/service is maintained in a structure known as a management information block. One way to access this information is with Performance Counters. See also Management Information Base.

single-threaded control
A model in which all objects are executed on a single thread.

sitename
See host name.

slow link
A modem connection, usually from 14,400 bps to 56,000 bps.

SMTP
See Simple Mail Transfer Protocol.

SNA
See Systems Network Architecture.

snap-in
Snap-ins are programs hosted within Microsoft Management Console (MMC) that administrators use to manage network services. The MMC provides the environment in which management tools (snap-ins) are hosted; snap-ins provide the actual management behavior necessary to administer network services such as IIS.

sniffer
See network sniffer.

SNMP
See Simple Network Management Protocol.

socket
An identifier for a particular service on a particular node on a network. The socket consists of a node address and a port number, which identifies the service. For example, port 80 on an Internet node indicates a Web server.

spider
A fast, automated program-such as a search engine, indexing program, or cataloging software-that requests Web pages much faster than human beings can. Other commonly used terms for spider are crawler and robot.

spoofing
Impersonating another person or computer, usually by providing a false e-mail name, URL, or IP address.

SQL
See Structured Query Language

SQL Access Group (SAG)
A consortium of vendors established in November 1989 to accelerate the Remote Data Access standard and to deliver protocols for interconnectivity among multiple SQL-based software products.

SSL
See Secure Sockets Layer.

Standard Generalized Markup Language (SGML)
An ISO standard (ISO 8879:1986) which supplies a formal notation for the definition of generalized markup languages. It is an international standard for the definition of device-independent, system-independent methods of representing texts in an electronic form. SGML is a metalanguage-that is, a means of formally describing a language, in this case, a markup language. See also Hypertext Markup Language; International Organization for Standardization; eXtensible Markup Language.

stateful object
An object that holds private state accumulated from the execution of one or more client calls.

stateless object
An object that does not hold private state accumulated from the execution of one or more client calls.

static binding
Binding (converting symbolic addresses in the program to storage-related addresses) that occurs during program compilation or linkage.

static page
HTML pages prepared in advance of the request and sent to the client upon request. This page takes no special action when requested. See also dynamic page.

stripe set
Refers to the saving of data across identical partitions on different drives. A stripe set does not provide fault tolerance; however, stripe sets with parity do provide fault tolerance. See also fault tolerance; partition; stripe sets with parity.

stripe sets with parity
A method of data protection in which data is striped in large blocks across all the disks in an array. Data redundancy is provided by the parity information. This method provides fault tolerance. See also fault tolerance; stripe set.

Structured Query Language (SQL)
The international standard language for defining and accessing relational databases.

stub
A routine that contains no executable code and that generally consists of comments describing what will eventually be there; it is used as a placeholder for a routine to be written later.

subnet mask
A TCP/IP configuration parameter that extracts network and host configuration from an IP address.

System Data Source Name (DSN)
A name that can be used by any process on the computer. IIS uses system DSNs to access ODBC data sources.

System Monitor
See Performance Monitor.

Systems Network Architecture (SNA)
A widely used communications framework developed by IBM to define network functions and to establish standards for enabling its different models of computers to exchange and process data. SNA contains separate layers. As changes occur in one layer, no other layer need be changed.

# T

T1
A U.S. telephone standard for a transmission facility at digital signal level 1 (DS1) with 1.544 Mbps in North America and 2.048 Mbps in Europe. The bit rate is with the equivalent bandwidth of approximately twenty-four 56 Kbps lines. A T1 circuit is capable of serving a minimum of 48 modems at 28.8 Kbps, or 96 modems at 14.4 Kbps. T1 circuits are also used for voice telephone connections. A single T1 line carries 24 telephone connections with 24 telephone numbers. When used for voice transmission, a T1 connection must be split into 24 separate circuits.

T3
A U.S. telephone standard for a transmission facility at digital signal level 3 (DS3). Equivalent in bandwidth to 28 T1s. The bit rate is 44.736 Mbps. T3 is sometimes called a 45-meg circuit.

TCP/IP
See Transmission Control Protocol/Internet Protocol.

telnet
A protocol that enables an Internet user to log onto and enter commands on a remote computer linked to the Internet, as if the user were using a text-based terminal directly attached to that computer. Telnet is part of the TCP/IP suite of protocols.

10BaseT
A variant of Ethernet which allows stations to be attached by a twisted-pair cable.

thin server
A client/server architecture in which most of an application is run on the client computer, which is called a fat client, with occasional data operations on a remote server. Such a configuration yields good client performance but complicates administrative tasks such as software upgrades. See also fat server.

thread
The basic entity to which the operating system allocates CPU time. A thread can execute any part of the application's code, including a part currently being executed by another thread. All threads of a process share the virtual address space, global variables, and operating-system resources of the process.

three-tier architecture
Divides a networked application into three logical areas: the user interface layer, the business logic layer, and the database layer. Layers may have one or more components. For example, there can be one or more user interfaces in the top tier, each user interface may communicate with more than one application in the middle tier at the same time, and the applications in the middle tier may use more than one database at a time. Components in a tier may run on a computer that is separate from the other tiers, communicating with the other components over a network.

throttling
Controlling the maximum amount of bandwidth dedicated to Internet traffic on a server. This feature is useful if there are other services (such as e-mail) sharing the server over a busy link.

thumbnail
A small version of a graphic with a hyperlink to a larger version of the same graphic.

time-out
A setting that automatically cancels an unanswered client request after a certain period of time.

token ring
A type of network with nodes wired into a ring. Each node constantly passes a control message (token) on to the next; whichever node has the token can send a message. Often, "token ring" is used to refer to the Institute of Electrical and Electronics Engineers (IEEE) 802.5 token ring standard, which is the most common type of token ring. See also local area network.

TP
See transaction processing.

transaction context object
An object used to allow a client to dynamically include one or more objects in one transaction.

transaction manager
A system service responsible for coordinating the outcome of transactions in order to achieve atomicity. The transaction manager ensures that the resource managers reach a consistent decision on whether the transaction should commit or fail.

transaction processing (TP)
The real-time handling of computerized business transactions as they are received by the system. Also called online transaction processing (OLTP).

Transmission Control Protocol/Internet Protocol (TCP/IP)
A communications standard for all computers on the Internet. On the sending end, TCP breaks the data to be sent into data segments. IP assembles segments into packets that contain data segments, as well as sender and destination addresses. IP then sends packets to the router for delivery. On the receiving end, IP receives the packets and breaks them down into data segments. TCP assembles the data segments into the original data set. See also packet.

tree, directory
A conceptual model used to describe the directory structure of a file directory or a Web site.

two-phase commit
A protocol that ensures that transactions that apply to more than one server are completed on all servers or none at all. Two-phase commit is coordinated by the transaction manager and supported by resource managers.

two-tier architecture
See client/server architecture.

type library
A binary file that describes a component's methods, properties, and data structure.

# U

UNC
See Universal Naming Convention.

Uniform Resource Locator (URL)
A naming convention that uniquely identifies the location of a computer, directory, or file on the Internet. The URL also specifies the appropriate Internet protocol, such as HTTP or FTP. For example: http://www.microsoft.com.

universal naming convention (UNC)
The naming convention used for physical directories.

upload
In communications, the process of transferring a copy of a file from a local computer to a remote computer by means of a modem or network. With a modem-based communications link, the process generally involves instructing the remote computer to prepare to receive the file on its disk and then wait for the transmission to begin.

URL
See Uniform Resource Locator.

URL directory
See virtual directory.

URL mapping
A term sometimes used for the process of associating a URL with a physical directory. See virtual directory.

usage data
Information the administrator can use to learn how other people are accessing and using a site. Analyzing this data helps an administrator identify a site's most popular (or unpopular) areas and clarifies the most common navigational paths through the site.

Usenet
The most popular news group hierarchy on the Internet.

user type
Assigned to an identifier in the metabase, a DWORD that specifies how data is used.

UTF-8
UTF-8 is a method of character encoding that allows for both single and multi-byte characters in one string, but UTF-8 files take up more space than files stored in an ANSI format. IIS supports Web files saved in UTF-8 format or ANSI format. See also codepage.

# V

VB
See Microsoft Visual Basic.

VBA
See Microsoft Visual Basic for Applications.

VBScript
See Microsoft Visual Basic Scripting Edition.

virtual directory
A directory name, used in an address, which corresponds to a physical directory on the server; sometimes called URL mapping.

virtual document
A term sometimes used for a document created automatically in response to information provided by the user; also called a dynamic document. A virtual document is created only in answer to a browser request, and is not permanently stored in a physical directory. An ASP page is an example of a virtual document.

virtual machine
Software that mimics the performance of a hardware device, such as a program that allows applications written for an Intel processor to be run on a Motorola processor.

Virtual Reality Modeling Language (VRML)
A language for coding three-dimensional HTML applications.

virtual server
Also called a Web site. A virtual computer that resides on an HTTP server but appears to the user as a separate HTTP server. Several virtual servers can reside on one computer, each capable of running its own programs and each with individualized access to input and peripheral devices. Each virtual server has its own domain name and IP address and appears to the user as an individual Web site or FTP site. Some Internet service providers use virtual servers for those clients who want to use their own domain names.

volatile objects
Typically, files that the Web site administrator updates frequently.

volume set
A combination of partitions on a physical disk that appear as one logical drive. See also logical drive.

VRML
See Virtual Reality Modeling Language.

# W

W3C
See World Wide Web Consortium.

WAN
See wide area network.

Web application
A software program that uses HTTP for its core communication protocol and delivers Web-based information to the user in the HTML language. Also called a Web-based application.

WebDAV
See Distributed Authoring and Versioning.

Web page
A World Wide Web document. A Web page typically consists of an HTML file, with associated files for graphics and scripts, in a particular directory on a particular computer (and thus identifiable by a URL).

Web server
In general terms, a computer equipped with the server software that uses Internet protocols such as HTTP and FTP to respond to Web client requests on a TCP/IP network.

wide area network (WAN)
A communications network that connects geographically separated areas.

Windows Internet Name Service (WINS) server
A server that uses the WINS protocol to map Internet Protocol (IP) addresses to user-friendly names. See also Domain Name System.

Windows Open Services Architecture (WOSA)
Standards for creating cross-platform applications that utilize Windows services.

Windows Script Host (WSH)
A language-independent scripting host for ActiveX scripting engines on 32-bit Windows platforms.

worker thread
A thread that is created by a component or ISAPI extension or filter to perform asynchronous processing. Using worker threads frees up IIS I/O threads to process additional requests.

working directory
A term sometimes used to describe the directory in which the Web server software is installed.

working set
The RAM allocated to a process in the Windows operating system.

World Wide Web (WWW)
The most graphical service on the Internet, the Web also has the most sophisticated linking abilities. It is a set of services that run on top of the Internet providing a cost-effective way of publishing information, supporting collaboration and workflow, and delivering business applications to connected users all over the world. The Web is a collection of Internet host systems that make these services available on the Internet using the HTTP protocol. Web-based information is usually delivered in the form of hypertext and hypermedia using HTML.

World Wide Web Consortium (W3C)
Founded in 1994 to develop common standards for the World Wide Web, the W3C is an international industry consortium jointly hosted by the Massachusetts Institute of Technology Laboratory for Computer Science (MIT/LCS) in North America, by the Institut National de Recherche en Informatique et en Automatique (INRIA) in Europe, and by the Keio University Shonan Fujisawa Campus in Asia. Initially, the W3C was established in collaboration with CERN, where the Web originated, with support from DARPA and the European Commission. For more information, see World Wide Web Consortium

WOSA
See Windows Open Services Architecture.

WSH
See Windows Script Host.

WWW
See World Wide Web.

# X

XML
See eXtensible Markup Language.

XSL
See eXtensible Stylesheet Language.

© 1997-2001 Microsoft Corporation. All rights reserved.