ASP (Active Server Pages)
| SSI based technology is limited to the range of commands/tags offered by the SSI-enabled web server provider. Web developers needed a way to embed dynamically interpreted code into HTML that can be processed by the web server on demand. Thus was born ASP. |
For example, what happens if you need to define operations not supported by the operating system (SSI-traditional) or the custom web server (SSI- Cold Fusion style)? What happens when you need to code your own tag logic?
What developers need is a way to embed dynamically interpreted code into HTML that can be processed by the web server on demand. That way every web site can develop its own set of custom tags.
What was needed was a hybrid CGI-SSI animal.
And thus was born ASP. ASP is a server extension of the IIS web server released by Microsoft (By the way, Apache does have MOD_ASP at this stage so that you can code ASP pages on Apache web servers. Also third party vendors also provide ASP functionality for non-IIS servers.). ASP allows developers to code custom tags in JavaScript (JScript) or VBScript. These tags can be interpreted by IIS before the pages are sent out.
| At about this time, by the way, Apache and ActiveState were making embedded Perl interpreters a reality. This meant that the overhead of loading the perl interpreter was no longer required. Perl with MOD_PERL is just as fast as ASP and provides all the same functionality. |
An ASP page at its core is simply a text file that has been named using the extension .asp and which contains HTML and scripting. Scripting, usually in VBScript provides a means to embed programmatic logic into HTML files that will be dynamically interpreted as the HTML page goes through the web server and also provides access to any server side object.
| NOTE: Like all server side technologies, functionality provided by ASP is completely cross-browser. All processing is done on the server side and the results of processing are displayed as plain HTML or images. Thus, a web developer can easily use the power of Excel or Power Point on the server side to generate graphs and charts that can be seen by a user running a UNIX-based web browser. |
Like SSI, ASP provides a means to specify a "tag" with instructions that should be interpreted by the web server. However, unlike SSI, ASP has a robust set of objects that you can use to do serious programming. It also gives you the ability to instantiate server side resources (any COM component). Consider the following simple ASP page:
<HTML>
<HEAD>
<TITLE>Test ASP</TITLE>
</HEAD>
<BODY>
<% @Language = "VBScript" %>
<% Response.Write("Hello cyberspace") %>
</BODY>
</HTML>
![[Simple ASP]](/old?u=http%3A%2F%2Fwdvl.com%2FAuthoring%2FTools%2FTutorial%2Fasp.gif&y=1999)
In the above example, you saw the "Response" object being used to print a message out to the web browser. ASP has a whole set of objects for the convenience of the application developer . These objects conveniently cover all key aspects of creating dynamic web pages.
The basic object hierarchy builds off the Scripting Context Object (which you will never really use itself) and looks something like the following:
Scripting Context Request Response Application Session Server
Contents:
COM and Active-X
Server-Side Java
Distributed Resources DCOM, CORBA, RMI
SSI Directives Cont.Introduction to the Web Application Development Environment (Tools)
COM and Active-X
