XML: It's Not Your Father's HTML | 4
XML on the Server
XML can be used on Web servers for two basic reasons. The first is to provide a standard way of wrapping database data to create custom content or for exchanging data between servers. The second is to add information to content to make it easier to share and syndicate.
Once you start sharing data or content between parties, they have to agree on the tags and what they mean. There are many industry groups that have gotten together to do just that. For example, there is a group working to define an XML/EDI standard for business transactions across the web. The Open Applications Group has recently defined a set of XML-based APIs for financial, manufacturing, and many other kinds of business data.
XML provides a useful wrapper for relational data, but it is mostly an "under the hood" technology, in the sense that it is automatically generated by one computer and consumed by another computer without being directly accessed by people. In this usage, XML is a new, more convenient and standard way of doing something that is already being done in other ways: sharing data that is stored in relational databases. Because XML is a standard, it saves everyone the trouble of deciding what format and syntax to use, and elminates the need to reinvent the basic processing tools with every new application.
XML's novelty is more apparent when we are talking about sharing other kinds of content. The need to do this is so strong that an industry group has submitted a proposal to the W3C called ICE (Information and Content Exchange) to define a standard (XML-based, of course!) for syndication. The ICE proposal is not restricted to any particular kind of content, but there are several groups working on creating industry-specific definitions, for everything from classified ads and real estate listings to electronic books to be sold and delivered over the Internet. Because XML describes the information and is in a standard format, consumers of the content can reliably extract its information and repurpose in their own sites.
XML is arriving on the scene just in time to enable these kinds of applications. But its benefits can only be realized if the content is valid, that is, it has the correct syntax and structure. Again, the right authoring tools can guarantee this.
Comments are welcome
Revised: February 16, 1999