XML-Watch Closely

I SPENT LAST WEEK at the XMLOne conference in Austin, TX. It was a great opportunity to catch up on one of the fastest growing technologies around. I spent most of my time at the conference, talking to attendees, presenters, and vendors. While at the show, IBM and Oracle announced additional support for XML and the Oasis xml.org site. At the same time, Microsoft was announcing further support for XML at their TechEd conference. At the end of the week, one thing was clear: You'd better become familiar with XML.

Currently, there are two main uses for XML. The first is as a technology for documents. XML provides a foundation for presentation-oriented publication (POP). With POP, you can store your basic text as multiple pieces in a database. The structure of a document is stored as a document type definition (DTD). The DTD defines the elements of a document and what they mean. You can then use stylesheets to control the formatting of the document. This is a powerful combination for manipulating documents. For example, using the same source, you can create different versions of a document for print, CD-ROM, or Web media. This is more efficient than saving three different versions of the same document. It also means it takes less work to keep them in sync. The key to POP is that the format and structure of information is kept separate from the information itself.

The second main use for XML is for data interchange. XML lets programs separate their understanding of data from the data itself. DTDs once again provide information about the structure and meaning of the data. The data itself is transferred between systems in XML format. This means that programs, when they are written, do not have to know as much about the data they use. The DTD makes it easy for the program to parse and understand the XML formatted data. The real value is that this approach reduces program complexity and minimizes the coupling between a program and its data. These are both very good things from a software engineering point of view.

XML for data interchange can be combined with other tools, such as message-oriented middleware (MOM), to create a powerful combination for enterprise application integration. This combination lets us create "smart data" for exchange between systems.

How soon should you start paying attention to XML? Sooner than you think. I'd planned on doing an XML project this year simply to become familiar with the technology, but events are leaving those plans in the dust. I now need to deploy an application that uses XML before the end of the year. I asked several pundits at the conference how quickly they see XML being adopted. All of them see an adoption curve at least as fast as Java. One prediction was for an adoption curve twice as fast as Java.