Unlike HTML, XML lets developers use different DTDs and define their own tags. Thus, developers can define arbitrary data structures. A movement is under way to establish XML as a standard way of defining all data interchange. There are also many industry-based efforts to define vertical vocabularies. Vertical vocabularies in the supply and purchasing processes could open up EDI to a wider variety of software solutions.
Similar efforts are possible in other vertical markets, such as financial services and health care.
Not just for the Web anymore XML is most famous for its connections to the Web, but DataChannel Corp., Microsoft and others provide programming tools for using XML in general-purpose programming situations. Ways of presenting data are inconsistently implemented. Some environments, such as Microsoft's Internet Explorer 4.0, support displays of raw XML data in a simple default presentation. Consequently, it's difficult for vendors to know what standard to follow if their XML applications have a presentation aspect, such as a Web-based application driven by underlying XML structures. Such applications lose the benefits of XML-based logic on the client, although they still take a load off the database server by allowing logic on the Web server or application server access to the structure of the data.