Schematron is a rule-based validation language for making assertions about patterns found in XML documents. It is a simple language which is based very much on XML itself and uses standard XPath to specify the assertion statements. The Schematron definations (a.k.a Schema) can be processed with standard XSL templates; which makes Schematron applicable is a variety of scenarios. Although a Schematron defination is referred as a Schema, but one must understand that Schematron differs in the basic concept from other schema languages; i.e. it is not based on grammars but on finding tree patterns in the parsed document. This approach allows many kinds of structures to be represented which could be difficult with grammar-based schema languages. For instance - imagine how would a typical schema be, for the following XML document - <?xml version="1.0" encoding="UTF-8"?> <instance> #### <person> ######## <fname/> ######## <lname/> #### </pers...