At Least One of Two Possible Elements

[Aki Yasuda]

I am trying to define an element that requires at least one of two elements. I have used the "all" compositor with the two elements as optional. This ensures that duplicate entries are not allowed; however, the parent element can be null.

<parent> - ALL - <child1> (optional)
|-<child2> (optional)

How do I make parent have at least one child?

[Scriptage]

What are you using here? DTD? Schema? XSLT?

[Aki Yasuda]

This is currently just an XSD (schema file)

[Scriptage]

Try:

<xs:group name="parentNode">
<xs:choice>
<xs:element name="child1" type="xs:string" maxOccurs="1" />
<xs:element name="child2" type="xs:string" maxOccurs="1" />
<xs:sequence>
<xs:element name="child1" type="xs:string" maxOccurs="1" />
<xs:element name="child2" type="xs:string" maxOccurs="1" />
</xs:sequence>
</xs:choice>
</xs:group>

I'm sure there's a better way to do it but this should do the trick.

[Aki Yasuda]

I placed the following my schema
<xs:group name="parentNode">
<xs:choice>
<xs:element ref="child1"/>
<xs:element ref="child2"/>
<xs:sequence>
<xs:element ref="child1"/>
<xs:element ref="child2"/>
</xs:sequence>
</xs:choice>
</xs:group>
<xs:element name="child1"/>
<xs:element name="child2"/>
And received a error: The content model of model group parentnode is ambiguous

[Scriptage]

What are you using to validate? The w3c validator shows no errors.

[Aki Yasuda]

XML Spy

[jkmyoung]

The choice should be:

<xs:choice>
<xs:sequence>
<xs:element name="child1" type="xs:string"/>
<xs:element name="child2" type="xs:string" minOccurs="1" />
</xs:sequence>
<xs:element name="child2" type="xs:string"/>
</xs:choice>

[Aki Yasuda]

Thanks

Slight modification to your suggestion works

<xs:element name="ParentNode">
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element ref="icms:child1"/>
<xs:element ref="icms:child2" minOccurs="0"/>
</xs:sequence>
<xs:element ref="icms:child2"/>
</xs:choice>
</xs:complexType>
</xs:element>
<xs:element name="child1"/>
<xs:element name="child2"/>


It requires at least one element under "ParentNode", permits both and does not allow duplicates. Interesting is that if both are present, they have to be in order: child1 and then child2 ... the reverse cause a validation error.