1. Information Retrieval and Web Design
Lecture (4)
Prepared by
Dr. Dunia Hamid Hameed

2. HTML
HTML (Hypertext Markup Language), This is a markup language (marks are inserted in the text) allowing us to represent rich content and to reference other resources (images, etc.), links to other documents (the most common feature of the WWW), display forms for subsequent processing etc.

3. History of web applications
Originally, the Web was simply a collection of static pages, documents, etc. that could be consulted and/or downloaded.
The next step in its evolution was the inclusion of a method to make dynamic pages allowing the displayed contents to be dynamic (generated or calculated from request data).

4. CGI
CGI (Common Gateway Interface) and defined a mechanism by which information could be passed between the HTTP server and external programs.

5. A brief History of the WWW
CGIs are still widely used because:
They are straightforward and most web servers support them.
They also give us complete freedom in choosing the programming language to develop them.

6. The operating schema of CGIs had a weak points:
Every time we received a request, the web server launched a process to run the CGI program.
In addition, because most CGIs were written in an interpreted language (PERL,Python etc.) or a language that required run-time environment (Visual Basic, Java, etc.), it represented a heavy load for the server machine, if the web had several CGI accesses, this led to serious problems.

7. alternatives to CGIs began to be developed to solve this serious performance issue. Two main solutions were devised: 1. Systems were designed for executing modules that were more integrated with the server so as to prevent the latter from having to instantiate and execute a multitude of programs. 2. The other solution was to equip the server with a programming language interpreter (RXML, PHP, VBScript, etc.) allowing us to include the pages in the code so that the server could execute them, thus cutting down response time.

8. All used one of the above two solutions but the most common and widespread were those that combined the two, i.e. an integrated programming language allowing the server to interpret commands that we "embed" in HTML pages and a system for executing programs more closely linked with the server that does not have the performance problems of CGIs.