trouble getting correct schema

[cmay]

I am beginning to wonder if it is not possible to get this working.

I am trying to do:

<root>
<a/>
<b/>
<c/>
</root>

With the following conditions:
1) a,b,c can be in any order
2) a and b can only be used 1 time
3) c can be used 0 to unbounded times.

Trying to do this with sequence, choice, all, each seem to miss one
part of the requirements.

Is this not possible?

 

[George Bina]

It is possible:

c*, (a, c*, b)|(b, c*, a), c*


<xs:element name="a"/>
<xs:element name="b"/>
<xs:element name="c"/>

<xs:element name="root">
<xs:complexType>
<xs:sequence>
<xs:element ref="c" minOccurs="0" maxOccurs="unbounded"/>
<xs:choice>
<xs:sequence>
<xs:element ref="a"/>
<xs:element ref="c" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="b"/>
</xs:sequence>
<xs:sequence>
<xs:element ref="b"/>
<xs:element ref="c" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="a"/>
</xs:sequence>
</xs:choice>
<xs:element ref="c" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>

Best Regards,
George

 

[cmay]

George,

Thanks for the reply and suggestion.

It looks like you are creating optional lists that depict the different
orders that could appear.

So while this might be doable for a,b,c the list would quickly grow out
of control if it were to expand from 3 possible elements to 10 or more.

Is that right?


Chris

 

[Joe Kesselman]

So while this might be doable for a,b,c the list would quickly grow out
of control if it were to expand from 3 possible elements to 10 or more.
Is that right?

Some constraints are better expressed in the application than in the schema.

 

[George Bina]

Hi Chris,

Yes, that is correct.
It is easy to create a more relaxed model and add these constraints at
some other level, at application level as Joe suggested or you can use
embedded Schematron rules inside XML Schema. You can find a working XML
Schema with embedded Schematron rules below.

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="a"/>
<xs:element name="b"/>
<xs:element name="c"/>

<xs:element name="root">
<xs:annotation>
<xs:appinfo>
<pattern xmlns="http://www.ascc.net/xml/schematron"
name="testRootContent">
<rule context="root">
<assert test="count(a)=1">a should be used 1 time.</assert>
<assert test="count(b)=1">b should be used 1 time.</assert>
</rule>
</pattern>
</xs:appinfo>
</xs:annotation>
<xs:complexType>
<xs:choice maxOccurs="unbounded">
<xs:element ref="a"/>
<xs:element ref="b"/>
<xs:element ref="c"/>
</xs:choice>
</xs:complexType>
</xs:element>
</xs:schema>

Best Regards,
George