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Schematron
Like XSD and Relax NG, a Schematron schema is an XML document which has the suffix “.sch”.An XML document can be validated against a Schematron schema using GUI-based tools such as XML ValidatorBuddy or Oxygen XML. There is also an XSLT stylesheet which implements Schematron validation, thus allowing the XML document to be dynamically validated by invoking any XSLT processor (eg. SAXON or XALAN).
XPath is heavily used in Schematron.
| This demonstrates co-constraints with <pattern>-<rule>-<assert>, progressive validation with <phase>, and <diagnostics>. |
| <?xml version="1.0"?> <superior rank="colonel" id="c123"> <subordinate rank="major" id="m456"> A subordinate must be ranked lower than the superior. </subordinate> </superior> |
| <?xml version="1.0"?> <schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding='xslt2' schemaVersion='ISO19757-3' defaultPhase="#ALL"> <phase><active pattern="CR"/></phase> <phase><active pattern="CS"/></phase> <pattern name="Check Subordinate" id="CS"> <rule context="superior"> <assert test="subordinate"> A superior must have a subordinate. </assert> </rule> </pattern> <pattern name="Check Rank" id="CR"> <rule context="subordinate[@rank='general']"> <assert test="/superior/@rank='general'"> A general's superior must be a general. </assert> </rule> <rule context="subordinate[@rank='colonel']"> <assert test="(/superior/@rank='general') or (/superior/@rank='colonel')" diagnostics="iColonel"> A colonel's superior must be a colonel or a general. </assert> </rule> <rule context="subordinate[@rank='major']"> <assert test="(/superior/@rank='general') or (/superior/@rank='colonel') or (/superior/@rank='major')" diagnostics="iMajor"> A major's superior must be a major, a colonel, or a general. </assert> </rule> </pattern> <diagnostics> <diagnostic id="iColonel"> Invalid <value-of select="@id"/>. </diagnostic> <diagnostic id="iMajor"> Invalid <value-of select="@id"/>. </diagnostic> </diagnostics> </schema> |
| A <rule> context specifies the XML fragments which should be checked against. The content for <assert> is the error message that will appear when the assertion fails. |
| The optional <phase> elements specify the order of validation. Here, the pattern “CS” will not be checked if the pattern “CR” failed. If no <phase> element is specified, all patterns will be checked against. <phase> elements should appear before any <pattern> element. |
| The optional <diagnostics> element contains error messages that are user-friendly to domain experts. It should appear after any <pattern> element. A <diagnostic> is invoked when an assertion fails. |
| This demonstrates cardinality and the use of a namespace. |
| <?xml version="1.0"?> <sentence xmlns="http://example.com/myNamespace"> Be polite! </sentence> |
| <?xml version="1.0"?> <schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding='xslt2' schemaVersion='ISO19757-3'> <ns prefix="n" uri="http://example.com/myNamespace"/> <pattern name="Language Filter"> <rule context="n:sentence"> <assert test="count(/n:sentence[contains(.,'fuck')])=0"> The sentence must not contain the word fuck. </assert> <assert test="count(/n:sentence[contains(.,'shit')])=0"> The sentence must not contain the word shit. </assert> </rule> </pattern> </schema> |
| This attaches some messages and demonstrates the third kind of validation – algorithmic validation. |
| <?xml version="1.0"?> <demography country="Malaysia"> <group race="Malay">60</group> <group race="Chinese">23</group> <group race="Indian">7</group> <group race="Others">10</group> </demography> |
| <?xml version="1.0"?> <schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding='xslt2' schemaVersion='ISO19757-3'> <title>Checking if the ethnic groups add up to 100%. </title> <pattern name="Demographic Make-up Check"> <title>Main check.</title> <p>The groups must add up to 100%.</p> <rule context="demography"> <assert test="sum(group) = 100"> The sum of the group proportions must be 100%. </assert> <report test="group"> Ethnic groups found. </report> </rule> </pattern> </schema> |
| <report> is the opposite of <assert>. It prints its content when the test passes during the validation process. |
| <title> is valid in <schema> and <pattern>. It provides a title. <p> is valid in <schema>, <pattern> and <phase>. It provides additional information. <emph> is valid in <active>, <assert>, <diagnostic>, <p> and <report>. It provides some emphasis. <span> is an inline element which can apply a stylesheet with the ‘class’ attribute. |
| Other elements which can enhance the appearance of the output are: <icon>, <fpi>, <flag>, <role>, and <subject>. |
| This illustrates the use of references. |
| <?xml version="1.0"?> <menu restaurant="Golden Outlet"> <dish>Satay</dish> <dish>Curry Chicken</dish> </menu> |
| <?xml version="1.0"?> <schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding='xslt2' schemaVersion='ISO19757-3'> <include href="menu.incl"/> <pattern name="Extends and uses an abstract rule."> <let name="v" value="//menu/@restaurant"/> <rule context="menu"> <extends rule="eod"/> <assert test="$v='Golden Outlet'"> The restaurant must be Golden Outlet. </assert> </rule> </pattern> </schema> |
| <!-- menu.incl --> <pattern name="Contains an abstract rule."> <rule abstract="true" id="eod" role="ExOfDish"> <assert test="dish"> There must be at least a dish. </assert> </rule> </pattern> |
| <include> treats the tag as if the content of the referenced file is at its place. |
| <let> can appear at the top of <schema>, <pattern> or <rule>. It is applicable only within that parent element |
| A <rule> declared as ‘abstract’ must be extended to be effective. |