HyperText Markup Language (HTML) is a simple markup system used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of applications. HTML markup can represent hypertext news, mail, documentation, and hypermedia; menus of options; database query results; simple structured documents with in-lined graphics; and hypertext views of existing bodies of information. HTML has been in use by the World-Wide Web (WWW) global information initiative since 1990. The HTML 3.0 specification provides a number of new features, and is broadly backwards compatible with HTML 2.0. It is defined as an application of International Standard ISO ISO8879:1986 Standard Generalized Markup Language (SGML). This specificiation will be proposed as the Internet Media Type (RFC 1590) and MIME Content Type (RFC 1521) called "text/html; version=3.0".
The Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers. A plain HTML document that the Web daemon retrieves is static, which means it exists in a constant state: a text file that doesn't change. A CGI program, on the other hand, is executed in real-time, so that it can output dynamic information.
For example, let's say that you wanted to "hook up" your Unix database to the World Wide Web, to allow people from all over the world to query it. Basically, you need to create a CGI program that the Web daemon will execute to transmit information to the database engine, and receive the results back again and display them to the client. This is an example of a gateway, and this is where CGI, currently version 1.1, got its origins.
The database example is a simple idea, but most of the time rather difficult to implement. There really is no limit as to what you can hook up to the Web. The only thing you need to remember is that whatever your CGI program does, it should not take too long to process. Otherwise, the user will just be staring at their browser waiting for something to happen.
Perl is a "Practical Extraction and Report Language" freely available for Unix, MVS, VMS, MS/DOS, Macintosh, OS/2, Amiga, and other operating systems. Perl has powerful text-manipulation functions. It eclectically combines features and purposes of many command languages. Perl has enjoyed recent popularity for programming World Wide Web electronic forms and generally as glue and gateway between systems, databases, and users.
Java, Sun Microsystems object programming language for creating platform-independent objects that can be sent over the Internet and securely run on a user's machine. Java(tm) is a simple, object-oriented, distributed, interpreted, robust, secure, architecture-neutral, portable, high-performance, multithreaded, dynamic, buzzword-compliant, general-purpose programming language. Java supports programming for the Internet in the form of platform-independent Java applets.
VRML, the virtual reality mark-up language, lets users log into a shared space, walk and talk together using chat features and, most importantly, build.