active server pages (ASP)

     many users think of Web pages as being like pages in  a book, stored intact on the server, ready to be flipped  through with the mouse. Increasingly, however, Web pages  are dynamic—they do not actually exist until the user  requests them, and their content is determined largely by  what the user requests. This demand for greater interactivity and customization of Web content tends to fall first on  the server (see client-seRveRcomputing and Web seRveR)  and on “server side” programs to provide such functions as  database access. One major platform for developing Web  services is microsoft’s Active Server Pages (ASP).

     In ASP programmers work with built-in objects that represent basic Web page functions. The RecordSet object can  provide access to a variety of databases; the Response object  can be invoked to display text in response to a user action;  and the Session object provides variables that can be used  to store information about previous user actions such as  adding items to a shopping cart (see also cookies).

     Control of the behavior of the objects within the Web  page and session was originally handled by code written  in a scripting language such as VBScript and embedded  within the HTmL text (see html and vbscRipt). However, ASP .NET, based on microsoft’s latest Windows  class libraries (see micRosoft .net) and introduced in  2002, allows Web services to be written in full-fledged  programming languages such as Visual Basic .NET and C#, although in-page scripting can still be used. This can  provide several advantages: access to software development tools and methodologies available for established  programming languages, better separation of program  code from the “presentational” (formatting) elements of  HTmL, and the speed and security associated with compiled code. ASP .NET also emphasizes the increasingly  prevalent Extensible markup Language (see xml) for organizing data and sending those data between objects using  Simple Object Access Protocol (see soap).

    Although ASP .NET was designed to be used with  microsoft’s Internet Information Server (IIS) under Windows, the open-source mono project (sponsored by Novell)  implements a growing subset of the .NET classes for use on  UNIx and Linux platforms using a C# compiler with appropriate user interface, graphics, and database libraries. 

     An alternative (or complementary) approach that has  become popular in recent years reduces the load on the  Web server by avoiding having to resend an entire Web  page when only a small part actually needs to be changed.  See ajax (asynchronous JavaScript and xmL).