• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

5. Important Concepts from the W3C RDF V... > 5.4. RDF Schema Alternatives

RDF Schema Alternatives

RDF isn’t the only specification related to describing schemas. XML documents (and their SGML predecessors) have long been validated through the use of Document Type Declarations (DTDs), described in the first release of the XML specification and still in heavy use. DTDs generally define how elements relate to one another within a schema; for example, they allow applications to check whether a specific element is required or one or more elements can be contained within another.

While useful for validating how elements within a schema relate to one another, DTDs have long had their critics. First of all, DTDs are based on a syntax totally unrelated to XML. This forces a person to become familiar with not one but two syntaxes in order to create a valid as well as well-formed XML document. The following DTD fragment defines an Items element, its child item, and the contents of item:


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint