<constraintSpec>

<constraintSpec> (constraint on schema) contains a constraint, expressed in some formal syntax, which cannot be expressed in the structural content model [22.4.4 Element Specifications]
Moduletagdocs — Documentation Elements
Attributesatt.global (@xml:id, @n, @xml:lang, @xml:base, @xml:space) (att.global.rendition (@rend, @style, @rendition)) (att.global.linking (@corresp, @synch, @sameAs, @copyOf, @next, @prev, @exclude, @select)) (att.global.analytic (@ana)) (att.global.facs (@facs)) (att.global.change (@change)) (att.global.responsibility (@cert, @resp)) att.identified (@ident, @predeclare, @module) (att.combinable (@mode) (att.deprecated (@validUntil)) ) att.typed (@type, @subtype)
schemesupplies the name of the language in which the constraints are defined
Status Required
Datatype 

<rng:ref name="data.enumerated"/>
data.enumerated
Legal values are:
schematron
(Schematron)
isoschematron
(ISO Schematron)
xsl
(XSLT)
private
(private constraint language)
Member of
model.oddDecl
Contained by
core: add corr del desc emph head hi item l meeting note orig p q quote ref reg said sic stage title unclear
dictionaries: case colloc def dictScrap entryFree etym form gen gram gramGrp hyph iType lang lbl mood number orth per pos pron stress subc syll tns usg xr
drama: camera caption castList epilogue performance prologue set sound tech view
figures: cell figDesc figure
header: change handNote licence rendition scriptNote tagUsage typeNote
iso-fs: fDescr fsDescr
linking: ab seg
msdescription: accMat acquisition additions collation condition custEvent decoNote filiation foliation layout musicNotation origin provenance signatures source summary support surrogates
spoken: writing
tagdocs: attDef classSpec elementSpec macroSpec schemaSpec specGrp
textcrit: lem rdg witness
textstructure: argument body div div1 div2 div3 div4 div5 div6 div7 docEdition epigraph imprimatur postscript salute signed titlePart trailer
transcr: damage metamark mod restore retrace secl supplied surplus
verse: rhyme
May contain
core: desc gloss
tagdocs: altIdent constraint equiv
Declaration

<rng:element name="constraintSpec">
 <rng:ref name="att.global.attributes"/>
 <rng:ref name="att.global.rendition.attributes"/>
 <rng:ref name="att.global.linking.attributes"/>
 <rng:ref name="att.global.analytic.attributes"/>
 <rng:ref name="att.global.facs.attributes"/>
 <rng:ref name="att.global.change.attributes"/>
 <rng:ref name="att.global.responsibility.attributes"/>
 <rng:ref name="att.identified.attributes"/>
 <rng:ref name="att.combinable.attributes"/>
 <rng:ref name="att.deprecated.attributes"/>
 <rng:ref name="att.typed.attributes"/>
 <rng:attribute name="scheme">
  <xhtml:dl class="valList"/>
 </rng:attribute>
 <rng:zeroOrMore>
  <rng:choice>
   <rng:ref name="model.glossLike"/>
   <rng:ref name="model.descLike"/>
  </rng:choice>
 </rng:zeroOrMore>
 <rng:optional>
  <rng:ref name="constraint"/>
 </rng:optional>
</rng:element>
element constraintSpec
{
   att.global.attributes,
   att.global.rendition.attributes,
   att.global.linking.attributes,
   att.global.analytic.attributes,
   att.global.facs.attributes,
   att.global.change.attributes,
   att.global.responsibility.attributes,
   att.identified.attributes,
   att.combinable.attributes,
   att.deprecated.attributes,
   att.typed.attributes,
   attribute scheme { text },
   ( model.glossLike | model.descLike )*,
   constraint?
}
SchematronRelationship between scheme attribute and contents: Schematron 1.x

<sch:ns prefix="s"
 uri="http://www.ascc.net/xml/schematron"/>
<sch:report test="tei:constraint/s:* and @scheme ne 'schematron'">Rules in the Schematron 1.* language must be inside a constraintSpec with a value of 'schematron' on the scheme attribute</sch:report>
SchematronRelationship between scheme attribute and contents: ISO Schematron

<sch:ns prefix="sch"
 uri="http://purl.oclc.org/dsdl/schematron"/>
<sch:report test="tei:constraint/sch:* and @scheme ne 'isoschematron'">Rules in the ISO Schematron language must be inside a constraintSpec with a value of 'isoschematron' on the scheme attribute</sch:report>
SchematronRelationship between scheme attribute and contents: XSLT

<sch:ns prefix="xsl"
 uri="http://www.w3.org/1999/XSL/Transform"/>
<sch:report test="tei:constraint/xsl:* and @scheme ne 'XSLT'">Rules in XSLT must be inside a constraintSpec with a value of 'isoschematron' on the scheme attribute</sch:report>
Schematron

<sch:ns prefix="sch"
 uri="http://purl.oclc.org/dsdl/schematron"/>
<sch:rule context="tei:macroSpec/tei:constraintSpec[@scheme='isoschematron']/tei:constraint">
<sch:report test="sch:assert|sch:report">An ISO Schematron constraint specification for a macro should not have an 'assert' or 'report' element without a parent 'rule' element</sch:report></sch:rule>
Example

This constraint uses Schematron to enforce the presence of the spanTo attribute (which comes from an attribute class) on the addSpan element:

<constraintSpec ident="demo-c1"
 scheme="isoschematron">
 <desc>Enforce the presence of the <att>spanTo</att> attribute</desc>
 <constraint>
  <sch:assert test="@spanTo">The spanTo= attribute of <sch:name/>
     is required.</sch:assert>
 </constraint>
</constraintSpec>
Example
<constraintSpec ident="demo-c2"
 scheme="isoschematron">
 <desc>Implement an accessibility rule which says that pictures should
   have textual explanations</desc>
 <constraint>
  <sch:report test="not(tei:figDesc or tei:head)"> You should
     provide information in a figure from which
     we can construct an alt attribute in HTML </sch:report>
 </constraint>
</constraintSpec>
Example

This constraint uses a language which is not expressed in XML to check whether the title and author are identical:

<constraintSpec ident="local"
 scheme="private">
 <constraint>
   (output = leq(title,author) "title and author cannot be the same")
 </constraint>
</constraintSpec>