Schematron - Xml format

Schematron is a xml format created in 1999.

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25Years Old

Schematron is a rule-based validation language for making assertions about the presence or absence of patterns in XML trees. It is a structural schema language expressed in XML using a small number of elements and XPath. In a typical implementation, the Schematron schema XML is processed into normal XSLT code for deployment anywhere that XSLT can be used. Read more on Wikipedia...

Schematron Wikipedia page
Schematron first developed in Academia Sinica

Example from the web:

<schema xmlns="http://purl.oclc.org/dsdl/schematron">
  <pattern>
     <title>Date rules</title>
     <rule context="Contract">
        <assert test="ContractDate &lt; current-date()">ContractDate should be
in the past because future contracts are not allowed.</assert>
     </rule>
  </pattern>
</schema>