4.5 Structure and data
A problem that is being increasingly experienced by internet companies is the fact that they have to interchange a large amount of data and that such data inherently lacks structure. For example, HTML has proved to be an enduring markup language for developing web pages; however, there are no facilities within the language, for example, to indicate whether an item of data, say a three-digit number, represents the price of a commodity or some hourly rate charged by a company employee.
There are also problems with browsers. There are two main browsers employed by users of the World Wide Web: Internet Explorer and Netscape Navigator. Each of these browsers can display the browser pages they process in different ways, especially if they contain advanced facilities of HTML.
There is also a further problem with browsers which is even more serious than the one detailed in the previous paragraph. Networking technologies are now being used in conjunction with other technologies such as those associated with mobile phone technology and television. This has led to the emergence of a number of different markup languages which are focused on particular devices, for example there is a markup language known as WML (Wireless Markup Language) which is used to display documents on internet mobile phones. The diversity of such languages means that the overhead in maintaining a number of versions of a document for different media can be very large.
Happily a technology has been developed known as XML which can be used to indicate structure in a document. There are also a number of tools available which allow the developer to maintain a single version of a document expressed in a language defined by XML and easily convert it into a form that can be displayed on a variety of media including television sets, internet phones and a variety of World Wide Web browsers.