Validating system model easter dating
As the XPath specification [XPath] shows, there are many possible kinds of relationship, known as 'axes'.While XML does include an ID/IDREF mechanism which allows for cross-referencing between elements, and hence another form of relationships, it only weakly binds those elements.Schematron is a useful and accessible supplement to other schema languages.The open-source XSLT implementation is based around a core framework which is open for extension and customisation.For example, we may select all Regular grammars, as used in DTDs, can then be viewed as tree patterns where the only available axis is the parent-child axis [Jelliffe1999e].Full use of tree pattern validation provides the maximum amount of freedom when modelling constraints for a schema.
The use of XML syntax provides additional flexibility through leveraging existing tools for markup manipulation, while the 'value added' features satisfy the requirements of developers looking for closer integration with databases and object-oriented languages.
Expressing validation rules using patterns is often easier than defining the same rule using a content model.
Tree patterns are collected together to form a Schematron schema.
A trivial XML vocabulary is introduced for the purposes of generating examples.
The later sections in this paper provides an overview of the open source XSLT framework used to implement the Schematron language.