Quite possibly, the most confusing aspect of XML Schemas and XML Schema authoring is that of Namespaces. You may recall from Chapter 5 that Namespaces were used pretty heavily in the schema examples we provided. Although implementing Namespaces themselves is trivial, keeping track of how those Namespace declarations impact your schemas and instance documents can be confusing.
Although XML Schemas make extensive use of Namespaces, this is because XML Schemas are, in fact, XML documents. Because DTDs have their own unique syntax, Namespace issues do not apply to DTDs at all because DTDs cannot make use of Namespaces.
There are three major issues that will confront most authors when dealing with Namespaces and XML ...