Value Arithmetic Required - Attributes (a co-constraint use case)

Require that the value of one attribute be greater than or equal to that of another attribute.

Cf. Value arithmetic required - elements, which supplies a similar use case involving elements (and unlike this use case actually does require arithmetic).

source: Joan Jesus Pujol Espinar [1]

Other use cases: Co-constraint Use Cases

Description

   If I declare two attributes named
   min and max, can I control that
   max<=min with a schema?

Note that the schema for schema documents has a similar constraint involving minOccurs and maxOccurs.

Analysis

FV

This is an OPERATION on two ATTRIBUTES raising a FLAG. Axis is attribute

CoConstraintDimensionSource:

CoConstraintDimensionDestination:

CoConstraintDimensionType:

CoConstraintDimensionEffect:

CoConstraintDimensionAxis:

Possible solutions

Relax NG

Schematron

Check clause

A possible check-clause solution:

 <xsd:complexType name="MinMax">
  <xsd:annotation><xsd:appinfo><sch:pattern><sch:rule>
      <sch:assert test="@min <= @max">
       The 'max' attribute must be at least as large as the 'min' attribute.
      </sch:assert>
     </sch:rule></sch:pattern></xsd:appinfo></xsd:annotation>
  <xsd:attribute name="min" type="xsd:int"/>
  <xsd:attribute name="max" type="xsd:int"/>
  <!--* ... *-->
 </xsd:complexType>

Conditional assignment

One of the possible solutions is:

<xsd:attributeGroup name="MinMax">
   <xsd:attribute name="min" type="xsd:int"/>
   <xsd:attribute name="max">
      <xsd:alt cond=". < ../@min" type="xsd:int"/>
      <xsd:alt                       type="xsd:error"/>
   </xsd:attribute>
</xsd:attributeGroup>

Conditional Type

<xsd:complexType name="MinMax">
   <xsd:alt cond="@max >= @min">
      <xsd:attribute name="min" type="xsd:int"/>
      <xsd:attribute name="max" type="xsd:int"/>
   </xsd:alt>
</xsd:complexType>