RELAX NG

DTD Compatibility Datatypes

DTD compatibility is both a library that checks the lexical spaces of its ID , IDREF , and IDREFS datatypes and a more expansive feature. This library adds to the normal RELAX NG processing and enforces DTD-like rules on the schema and on the instance document. This package is designed to facilitate the transition from DTDs to RELAX NG by emulating the attribute types ID, IDREF, and IDREFS. The DTD compatibility feature checks whether ID values are unique within a document and that IDREF and IDREFS are references or whitespace-separated lists of references to ID values defined in the document. It also checks the schema itself to ensure that datatypes are used only in attributes. Unlike their W3C XML Schema counterpart, these datatypes have no facets.

That’s pretty much all you have to know about this library. Let’s use it straightaway to define the id attributes in our library:

<element xmlns="http://relaxng.org/ns/structure/1.0" name="library" datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"> <oneOrMore> <element name="book"> <attribute name="id"> <data datatypeLibrary="http://relaxng.org/ns/compatibility/datatypes/1.0" type="ID"/> </attribute> <attribute name="available"> <data type="boolean"/> </attribute> <element name="isbn"> <data type="NMTOKEN"> <param name="pattern">[0-9]{9}[0-9x]</param> </data> </element> <element name="title"> <attribute name="xml:lang"> <data type="language"> <param name="length">2</param> </data> </attribute> ...