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MULTI-SCHEMA XML VALIDATOR SCHEMATRON ADD-ON

The Multi-Schema XML Validator Schematron add-on is a Java tool to validate XML documents against RELAX NG [1] schemas annotated with Schematron schemas [2]. This release includes software developed by the Apache Software Foundation [3]

Overview

By using this tool, you can embed Schematron constraints into RELAX NG schemas. Then this tool validates documents against both RELAX NG grammar and embedded schematron constraints. Schematron makes it easy to write many constraints which are difficult to achieve by RELAX NG alone.

To validate documents with Schematron-annotated RELAX NG grammar, enter the following command:

    java -jar relames.jar MySchema.rng doc1.xml [doc2.xml ...]

To run the program, you must have Xalan-Java [4] and JAXP-compliant XML parser in your classpath.

How to embed Schematron

This release supports Schematron constraints to be embedded in the <element> pattern of RELAX NG:

<define name="foo" xmlns:s="http://www.ascc.net/xml/schematron">
  <element name="foo">
    <!-- content model definition in RELAX NG, as usual -->
    ...

    <!-- embedded schematron constraints -->
    <s:assert test="@min < @max">
      the max attribute must be greater than the min attribute.
    </s:assert>
    <s:assert test="count(*)>1">
      at least one child element is necessary.
    </s:assert>
    <!-- as many as you want -->
  </element>
</define>

In this example, for every "foo" element, two assertions are checked. In general, validation is performed in the following way: whenever an element mathces a pattern, schematron constraints are checked for that element.

In plain Schematron, a <rule> element determines the context node against which those assertions are evaluated. In Schematron-annotated RELAX NG, on the other hand, the element that matches the <element> pattern will become the context information instead.

Relames also supports the use of <rule> elements in RELAX NG grammar.

<define name="root" xmlns:s="http://www.ascc.net/xml/schematron">
  <element name="root">
    <!-- content model definition in RELAX NG, as usual -->
    ...

    <!-- for any hotel element found within this element -->
    <s:rule context="hotel">
      <s:assert test="count(*)>1">
        at least one child element is necessary.
      </s:assert>
    </s:rule>
  </element>
</define>

First, nodes that match the context attribute are computed. Then assertions are tested for each node.

Relames can also handle Schematron's <pattern> element --- it basically just ignores the <pattern> element itself and process <rule>s in it directly.

Relames also handles Schematron's <ns> element. They can appear in anywhere in the RELAX NG schema, and they affect other schematron elements that appear as descendants of siblings. IOW, the following works:

 <element name="foo">
   <s:ns prefix="abc" uri="..." />
   <s:report test="abc:someNode" ... />
   <element name="child">
     <s:report test="abc:someNode" ... />
     ...
   </element>
 </element>

For the backward compatibility with earlier versions of relames, Namespace prefixes found in XPath expression (like the one above) are also resolved through xmlns declarations in the grammar file, if it's not declared by <s:ns>. Note that the default namespace is bound to the URI declared by the ns attribute of RELAX NG. Consider the following example:

<grammar xmlns="http://relaxng.org/ns/structure/0.9"
         xmlns:foo="http://www.example.org/foo"
         ns="http://www.sun.com/xml">
  <start xmlns:s="http://www.ascc.net/xml/schematron">
    <element name="foo">
      <!-- content model definition in RELAX NG, as usual -->
      ...

      <s:assert test=" foo:abc | def ">
        ...
      </s:assert>
    </element>
  </start>
</grammar>

The XPath expression "foo:abc|def" will match {http://www.example.org/foo}abc elements and {http://www.sun.com/xml}def elements. Note that "def" does NOT match elements with the namespace URI of "http://relaxng.org/ns/structure/0.9".

This release supports , and of Schematron 1.3 and and of Schematron 1.?. You can write as many constraints as you want in one pattern.

Annotated RELAX NG grammars are still interoperable in the sense that other RELAX NG processors will silently ignore all Schematron constraints.

Using from Command Line

The jar file can be used as a command-line validation tool. Type as follows:

    java -jar relames.jar

To get the usage screen.

Using from your Program

The schematron extension can be used through JARV API [5], which makes it very simple to use this library from your application.

When you call the VerifierFactory.newInstance method, type as follows:

VerifierFactory factory = VerifierFactory.newInstance( "http://relaxng.org/ns/structure/1.0+http://www.ascc.net/xml/schematron");

to create a verifier factory from this extension library.

Limitation

  • id() function works correctly only if Xerces or Crimson is used as the DOM implementaion. This is because of the limitation in W3C DOM.

References

[ 1] RELAX NG https://www.oasis-open.org/committees/relax-ng/
[ 2] Schematron https://www.schematron.com/
[ 3] Apache Software Foundation https://www.apache.org/
[ 4] Xalan-Java https://xml.apache.org/xalan-j/
[ 5] JARV API http://iso-relax.sourceforge.net/JARV/