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Co-occurrence constraints in XML Schema |
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Schematron |
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Processing model |
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Writing rules |
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Embedding Schematron in XML Schema |
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XML Schema can't articulate certain kinds of
constraints: |
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When an element's type depends on an attribute
value |
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When an element's content depends on the
presence of an attribute |
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When the text in mixed content has to be a
certain type |
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When a value has to match an ID in a separate
document |
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When an element can contain repeatable elements
in any order |
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Schematron can be used to plug the gaps |
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Rule-based schema language |
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Asserts conditions that elements/attributes must
or must not fulfil |
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Built on top of XSLT |
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Schematron schemas are transformed into XSLT
stylesheets |
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Constructed stylesheet produces validity report |
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Style of validity report depends on how the
stylesheet was created |
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Schematron namespace is http://www.ascc.net/xml/schematron |
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Usually associated with prefix sch |
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Schematron schema made up of patterns |
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Named collections of similar rules |
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e.g. pattern for "structure", pattern
for "data" |
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Patterns operate in parallel |
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Can define phases to combine different patterns |
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Patterns contain a number of rules |
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Defined with sch:rule |
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Each rule matches a particular set of nodes |
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identified through XSLT pattern in context
attribute |
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Inside each rule are a number of sch:assert and sch:report
elements |
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Assertions are positive (things that must be
true) |
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Reports are negative (things that should be
reported if they occur) |
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Test is XPath expression held in test attribute |
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Content gives description to be passed to
validator |
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Schematron patterns (sch:pattern) can be
embedded in any xs:appinfo within an XML Schema schema |
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Topologi's Schematron validator |
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Extracts Schematron schema |
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Can configure extraction routine |
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Validates against XML Schema schema |
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Validates against Schematron schema |
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Can configure which meta-stylesheet is used, and
therefore what kind of report you get |
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Schematron is very useful for "plugging the
gaps" in XML Schema |
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Use to express constraints over and above those
allowed in Schematron |
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Schematron schemas contain patterns |
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Patterns are named and contain rules |
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Rules have a context and contain assertions and
reports |
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Assertions and reports have tests and contain
descriptions or error messages |
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Schematron patterns can be embedded in XML
Schema schemas |
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Add Schematron rules to the schema to express
additional constraints |
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Notes
