View source for Value equality - and following siblings

= Value equality - and following siblings (a co-constraint use case) =

Make the content model depend on the value of a particular child
element.  (In this case, only the following part of the content
model need vary.)

source: Valeri Gavrilovets
[http://lists.w3.org/Archives/Public/xmlschema-dev/2002May/0053.html]

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Other use cases: [[Co-constraint Use Cases]].

== Description ==

The schema should describe two distinct kinds of possible documents:


<pre><nowiki>
         <result type="java.util.Hashtable">
            <STATUS>OK</STATUS>
            <Key1>123</Key1>
            <Key2>234</Key2>
            <Key3>324</Key3>
            <Key4>256</Key4>
         </result>
</nowiki></pre>

and

<pre><nowiki>    
         <result type="java.util.Hashtable">
            <STATUS>INIT</STATUS>
            <ERROR>200</ERROR>
         </result>
</nowiki></pre>


== Analysis ==

(Add your analysis here; see your name in pixels!)

=== MSM ===
It's hard to escape the feeling that this would be better done by
specifying distinct status_ok and status_nok elements.  If there
are reasons why that would not work in some situations, I'm having
trouble identifying them.

If we removed the Element Declarations Consistent constraint,
I suppose one could write something like this:

<pre><nowiki>
 <xsd:complexType name="result">
  <xsd:choice>
   <xsd:sequence>
    <xsd:element name="STATUS">
     <xsd:simpleType>
      <xsd:restriction base="xsd:NMTOKEN">
       <xsd:enumeration value="OK">
       </xsd:enumeration>
      </xsd:restriction>
     </xsd:simpleType>
    </xsd:element>
    <xsd:element ref="key1"/>
    <xsd:element ref="key2"/>
    <xsd:element ref="key3"/>
    <xsd:element ref="key4"/>
   </xsd:sequence>

   <xsd:sequence>
    <xsd:element name="STATUS">
     <xsd:simpleType>
      <xsd:restriction base="xsd:NMTOKEN">
       <xsd:enumeration value="INIT">
       </xsd:enumeration>
      </xsd:restriction>
     </xsd:simpleType>
    </xsd:element>
    <xsd:element ref="ERROR"/>
   </xsd:sequence>
  </xsd:choice>
 </xsd:complexType>
</nowiki></pre>


== Possible solutions ==

=== Relax NG ===
=== Schematron ===
=== Check clause ===
=== [[SchemaPath]] ===
=== Conditional Type ===

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[[Category:CoConstraintUseCase]]