Wireless Application Protocol (WAP) itself is described in the User Tech section. This section only concerns itself with how WAP works.
The language
WAP uses a subset of XML, called Handheld Device Markup Language (HDML) or Wireless Markup Language (WML), similar to a cut-down version of HTML. Instead of pages, WAP uses cards arranged in stacks, and they are designed to pass the information concisely and quickly.
The architecture
Normally, web pages are stored on the hard discs of web (http) servers, or in databases linked to the web servers. The same arrangement applies for WAP, except that there is another layer, the WAP gateway which converts HTML content to WML/HDML where necessary. This can be running on the same machine as the server, or somewhere far away: even on the other side of the world. Some WML content is pre-compressed to reduce the data passed to the browser.
WAP allows the “soft keys” on the browser to be altered, and has some scripting support, and is a fascinating subject in itself. It isn’t explained further on this site, but www.wapforum.org is a good place to start looking for more information.
Normally, the data is transferred using a standard data connection, as would be used for any web browsing, and it is not necessary to use the WAP gateway provided by the ISP you are dialled into, or for the ISP to be related to the mobile phone network.
The history
There was a previous version of WAP (obsolete before it launched) that used SMS to transfer WAP information, but this is also very similar to the new information services being provided by means of the SIM toolkit that some mobile handsets use: this allows information menus to be created, so the user can request information using them. Not strictly WAP, but very similar indeed. The trouble with this idea is that at the time of writing, the cost of sending each SMS is too high to make the many SMS messages you’d need affordable.
The future
Despite a shaky start, largely caused by advertising hype, WAP has a huge potential. It is poised to use whatever data channels are available, and it is likely that it will be a huge information resource for users. The technical infrastructure it is carried over is changing, and the concept of “information anywhere” is likely to prove a winner!