= General component schema Schematron rules =

This page concerns a proposal to extend the [source:/metadata/trunk/toolkit/general-component-schema.xsd general component schema] with a number of [http://www.schematron.com/ Schematron] rules to specify certain restrictions that cannot be expressed using plain XSD.

Currently a version of this extended schema can be found as a part of the testing resources of the CMDValidate library of the [[ComponentRegistryAndEditor|ComponentRegistry]]: 

* [source:/ComponentRegistry/trunk/CMDValidate/src/test/resources/schema/general-component-schema.xsd general component schema extended with schematron rules]

== Restrictions ==

=== Sibling components or elements should all have a different name ===

{{{
#!xml
<sch:pattern id="component" name="CMD component group">
    <sch:rule context="CMD_Component|CMD_Element">
	<sch:assert test="empty(preceding-sibling::*[@name=current()/@name])">Sibling components or elements should all have a different name. Found multiple components or elements named '<sch:value-of select="@name"/>'!</sch:assert>
    </sch:rule>
</sch:pattern>
}}}

=== Attribute name shouldn't be 'ref' or '!ComponentId' ===

{{{
#!xml
<sch:pattern id="attribute" name="CMD attribute">
    <sch:rule context="Attribute">
	<sch:assert test="empty(preceding-sibling::Attribute[Name=current()/Name])">All attributes in an attribute list should have a different name. Found multiple attributes named '<sch:value-of select="Name"/>'!</sch:assert>
	<sch:assert test="not(Name=('ref','ComponentId'))">Attribute name shouldn't be 'ref' or 'ComponentId', as these are used internally by CMD!</sch:assert>
    </sch:rule>
</sch:pattern>
}}}

=== All items in an enumeration should be different ===
{{{
#!xml
<sch:pattern id="item" name="CMD enumeration item">
    <sch:rule context="item">
	<sch:assert test="empty(preceding-sibling::item[.=current()])">All items in an enumeration should be different. Found multiple items with value '<sch:value-of select="."/>'!</sch:assert>
    </sch:rule>
</sch:pattern>
}}}