So far, we have looked at a number of technologies that are all directly related to the XML Recommendation or extend XML in some way. However, there is another category of XML technologies called XML vocabularies. These are individual markup languages that have been written using XML 1.0.
XML vocabularies can be treated just like any other XML document, because they are well-formed (and in many cases, valid) XML. When you are developing XML documents, what you are really doing is developing your own XML vocabularies. However, there may already be an existing XML vocabulary that will meet your needs.
XML vocabularies are also sometimes referred to as XML applications. To avoid confusion, we've tried to use the term ...