Active Server Pages - Glossary

Core Components which make up an ASP.NET Application

ADO

ActiveX Data Objects. ADO is a set of objects you can use to interact with database managers. The objects enable you to retrieve records with a database query and update existing records with new values. You can easily use ADO with ASP through the ADO component.

API

Application Programming Interface. A set of properties and methods made available by a system to the outside world. The underlying system might change, but if the API does not change then systems which use the API also don't need to be revised.

Application object

An ASP built-in object which represents the common information shared by all concurrent users of an application. An application is the set of all ASP files in a virtual directory and its subdirectories.

Application variables

A variable defined in the global.asa file, which can be read by any ASP script in the same virtual directory as the global.asa file.

Array

A placeholder which can hold more than one value. A variable that stores other variables in a particular order. Each variable in an array can be accessed by its index. For example, SomeArray[12] is the element at index 12. Some languages number arrays from 0, whereas others start at 1. Thus, SomeArray[12] could be the 12th or 13th element depending on the array's first element.

Associative array

A two-dimensional array that stores the name of a value (such as "FileName") and its associated value ("inventory.mdb").

Browser-server interaction

The dialog between a client (usually a Web browser) and a Web server, which consist of a series of requests and responses.

CGI

Common Gateway Interface. An NCSA standard for communicating between a Web server and other applications.

Client

A system which requests resources from a server, or the program requesting such services. For example, a Web client is typically a Web browser, but could include other applications as well.

Client-side

Running on a client, rather than a server. For example, a Java applet embedded in an HTML page runs on the client computer, not the server that sends out the page.

Collection

A variable that can be accessed either by index (like an array), or by key. In Perl, a collection is called an associative array.

Component

In Microsoft-speak, an object that provide some functionality, but doesn't have a graphical user interface. Components are designed to be used on Web servers, where nobody would see a graphical user interface.

Constant

A placeholder that is assigned a single, unchanging value.

Cookie

A small chunk of data that is initially sent by a server to be stored on a client's machine. Subsequent requests from that client are sent along with previously-defined cookies and their values. For example, a user's username and password might be stored in cookies, so that the user doesn't have to enter them every time to access a protected resource.

Data source

An ODBC datasource is link from the outside world to a particular database using a database manager. You must set up an ODBC data source to use a database with ADO, and hence, with ASP. You can set up a data source with the ODBC control panel.

Database manager

A database manager (also known as a DBMS, or database management system) is a program for administering and manipulating databases. Microsoft Access is a database manager, as are Oracle and SQL Server.

Delimiter

A character that separates one datum from the next.

DSN

Data source Name. The name, defined at the time the datasource is created, which is used to identify a particular ODBC datasource. There are User, System and File DSNs, each of which is visible to different ODBC clients. With ADO, you must set up a System DSN (which is visible to all users).

ECMAScript

The ECMA standard for an Internet scripting language (a.k.a. ECMA Standard 262). The standard is based on Netscape's JavaScript.

Encoding

On the Web, encoding usually means translating one character set into another. For example, the HTML specification doesn't allow for angle brackets (< and >) to be embedded directly into text because of their special meaning within HTML. Instead, HTML encoding specifies that they be translated to < and >, respectively.

Event

Things that happen in the world and are recognized by a program or object. For example, a mouse click is an event recognized by some objects but not others.

Expression

A combination of variables, constants, and operators that produces a value.

FastCGI

A newer version of CGI which addresses some of the performance problems with CGI, but it's not available with all Web server software.

Glossary

Each time you click a glossary term, you'll see a window like this displaying the term and its definition. To see the entire glossary, click "Show All Terms."

Host

Generally, any networked computer. In the case of a URL, it's the computer-name portion of a URL.

HTTP

HyperText Transfer Protocol. The conventions for exchanging information over the Web, which are defined by the World Wide Web Consortium.

HTTP headers

Additional information which is sent back and forth between a Web client and HTTP server. The additional information might include the last modified date of a file sent by a server, or a cookie sent by a client. In a web response (sent by the server) the headers are sent before any HTML.

Include file

A file with user-defined functions to be used in more than one ASP script. The file is referenced ("included") in the script, allowing the script to use the code in the included file as if it were part of the scriptitself.

Index

When referring to arrays or collections, the index identifies the element within the array or collection. For example, an array of T-shirts could be referenced by index as concertShirts(11), which is the item at index 11 in the array. Occasionally, index will be used to refer "the index file" of a Web server directory. The index file (usually either index.html on Unix, or Default.htm on Windows) is the file returned when a browser requests the directory which the index file resides in, rather than any particular file within the directory. For example, http://some.webserver.com/catalog/ will usually refer to the index file (for example, index.html) within the catalog directory.

ISAPI

Internet Server API. Microsoft's API for integrating software directly into Internet Information Server.

Java

A programming language designed by Sun, which is popular for building Web applications. In the past, Java has been limited to the client-side, but some Web server software now supports Java servlets.

JavaScript

Originally Netscape's scripting language, which is intended to comply with the ECMAScript standard. JavaScript is a popular language for client-side scripting. ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known implementations such as JavaScript, JScript and ActionScript.

JScript

Originally, Microsoft's clone of JavaScript, but now an implementation of the ECMAScript 262 standard for a Web scripting language. It's still very similar to JavaScript, which Netscape has promised will also conform to ECMAScript 262.

Key

A key specifies a particular element within a collection. For example a collection of first names might use a last name as a key, and Bill Bobo's first name could be retrieved with: FirstNames("Bobo").

Method

An action which can be performed by an object. For example, ASP's Response object has a Write() method, which can write text to an HTML response as it's sent to a requesting client.

NSAPI

Netscape Server API. Netscape's API for integrating software directly into Netscape Web server software.

Object

In object-oriented programming, an instance of a class. Usually combines both internal state (data) and procedures (called methods).

ODBC

Object Database Connectivity. ODBC is a Microsoft standard for accessing databases through a database manager, both locally and remotely. To use ODBC with ASP, you must set up an ODBC connection for the desired database.

OLE

According to Microsoft, OLE no longer stands for Object Linking and Embedding, but that's what it enables. With OLE, objects can communicate with one another and use each other's capabilities. For example, if you follow a link in Internet Explorer to a PowerPoint presentation, Internet Explorer will display the PowerPoint presentation within the browser window, as though it were HTML.

OOP

Object-oriented programming. A style of programming which is based on object-oriented analysis and design. The most obvious characteristic is that systems are based on objects, which incorporate both actions (methods) and data.

Path

The series of directories (or folders) from a file system's top-level to a directory or file. Different systems use different characters to separate directories within a path, but the Web standard is a forward slash (/), for example: /catalog/spring-98/.

Perl

The Practical Extraction and Report Language is a popular interpreted language used for scripting and system administration tasks. Many CGI programs are written in Perl.

Port

An additional network specifier which identifies a particular network connection on a computer. Some ports are reserved for specific services such as a POP3 server (110), or HTTP (80), but most Web server software will allow you to associate a site with any unused port. Ports identify logical, rather than physical, connections to a machine. In a URL, the port is specified following a colon (:) immediately after the computer name or address.

Primary key

A field (or group of fields) with a unique value in each row of a database table.

Procedural programming

A style of programming centered on actions performed by procedures. The C language is probably the most popular procedural language, while C++ is its object-oriented counterpart.

Property

A characteristic of an object. For example, a Font object might have a Size property, which would store the point size of the Font. Although some properties are read-only, many properties can both be read and set to new values.

Query

An information request. Usually query means a request for data from a database, and is processed by a database manager which returns a result.

Query string

The portion of a URL which follows the question mark character (?), which is usually used to pass additional information to the server. For example, a search string could be sent to the URL of a search engine as the query string within a URL.

Record

A row in a database table.

Recordset

A group of database table records that has been read into an ASP script.

RecordSet object

The ASP object used to hold and manipulate records read from a database.

Request object

An ASP built-in object which represents the client's request to the Web server, and includes such items as cookies and information on the client's browser.

Response object

An ASP built-in object which represents the Web server's response to a client's request, and includes such items as the last modified date for a requested page and new cookie values.

Schedule file

A file which holds instructions for the order and/or frequency that ads will appear in the Ad Rotator Component.

Script

A short program which is usually interpreted, rather than compiled.

Scripting engine

A software program which enables some Microsoft software (scripting hosts, such as Internet Explorer or Internet Information Server) to understand a scripting language.

Scripting language

Usually an interpreted programming language which is used for writing short programs to run on both clients and servers. Scripting languages often have a limited ability to protect clients from malicious or buggy programs.

Server

A system which offers resources to other computers. For example, services might include files, computational power or printing. On the Web, servers run a Web server process which accepts and replies to HTTP requests.

Server object

An ASP built-in object which represents the Web server. The server object's most important job is to create new objects (other than the ASP built-in objects). For example, the CreateObject() method enables you to build an ADO object from the ADO Component, which can then be used for database access within a script.

Server variables collection

A series of values representing the properties of a Web server (e.g., operarting system, software version, file system etc.).

Server-side

Running on a server, rather than client. ASP is a server-side technology because the scripts run on the Web server, rather than on a client's computer.

Session

A user's connection to a Web server.

Session management

Controlling the interaction between a client and server throughout a session. With CGI, this can be messy and involves such chicanery as stuffing session values into hidden fields. ASP makes session management much easier by including a Session object which stores session values for each user for the duration of the user's session.

Session object

An ASP built-in object which represents a user's session with a Web server. Session values are specific to each user and maintained throughout that user's session. The session includes all the interactions until the session is ended in a script, or times out.

State

The internal condition of an object or dialog. HTTP is basically a stateless protocol, which means that each new connection from client to server is independent of previous connections, i.e. the Web server forgets everything after each connection.

Substring

A portion of a character string (e.g., "shirt" is a substring of "t-shirt").

Third-party components

Software modules sold by independent vendors that add functionality to ASP.

Uninitialized [variable value]

A variable that has no value assigned to it.

URL

Uniform Resource Locator. A naming convention for identifying the location of network resources, which is of the form: protocol://host:port-number/path/file[?querystring]

Variable

A placeholder that can hold any value of a particular type.

VBScript

A scripting version of Microsoft's Visual Basic family. VBScript is less powerful than Visual Basic for Applications or full-blown Visual Basic. VBScript has similar capabilities to JScript.

Virtual directory

A directory which appears to exist when accessing the Web server, but might have a different structure in reality. For example, the top-level (or root) directory is usually virtual because to the Web server it's simply / (the root directory), but on the underlying computer the directory might actually be: E:\Web\IIS\WebRoot\.

Web application

An application which is deployed over the Web, and maintains an interaction between a client and server.

Web server

A system which accepts and processes HTTP requests.

Web transaction

A transaction is an action that is designed to be atomic: even if there are discrete steps within a transaction, either all the steps happen or none of them do. For example, to transfer money from one bank account to another account, you would want to withdraw from the first account and deposit to the second. If the deposit fails (perhaps because the second account number was invalid), then you want to undo (a.k.a. rollback) the withdrawal. Managing transactions over the Web is a hot topic, and Microsoft offers the Transaction Server for just monitoring transactions.