View source for Value arithmetic required - attributes

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= 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
[http://lists.w3.org/Archives/Public/xmlschema-dev/2001Nov/0043.html]

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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
{| border="1" cellpadding="2" cellspacing="0"
|  [[CoConstraintDimensionSource]]: 
|-
|  [[CoConstraintDimensionDestination]]: 
|-
|  [[CoConstraintDimensionType]]: 
|-
|  [[CoConstraintDimensionEffect]]: 
|-
|  [[CoConstraintDimensionAxis]]: 
|}

== Possible solutions ==

=== Relax NG ===
=== Schematron ===
=== Check clause ===
A possible check-clause solution:

<pre><nowiki>
 <xsd:complexType name="MinMax">
  <xsd:annotation><xsd:appinfo><sch:pattern><sch:rule>
      <sch:assert test="@min &lt;= @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>
</nowiki></pre>

=== Conditional assignment ===
One of the possible solutions is: 


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

</nowiki></pre>


=== Conditional Type ===


<pre><nowiki>
<xsd:complexType name="MinMax">
   <xsd:alt cond="@max &gt;= @min">
      <xsd:attribute name="min" type="xsd:int"/>
      <xsd:attribute name="max" type="xsd:int"/>
   </xsd:alt>
</xsd:complexType>

</nowiki></pre>


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[[Category:CoConstraintUseCase]]