Either element or attribute in XSD

[gisleyt]

Is it possibly to specify that I want a either a element or an
attribute to occur, but not both at the same time?

<xs:complexType name="foo">
<xs:sequence>
<xs:element minOccurs="0" ref="bar"/>
</xs:sequence>
<xs:attribute name="bar" default="" type="xs:anyURI"/>
</xs:complexType>

In this complexType I don't want both the element "bar" and the
attribute "bar" to be present, only one of them. Can I express this in
any way in xsd?

-Gisle-

[George Bina]

Hi,

No, you cannot do that in XML Schema alone. You can do that with
embedded Schematron rules inside XML Schema. Here it is a working
example:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="foo" type="foo">
<xs:annotation>
<xs:appinfo>
<pattern xmlns="http://www.ascc.net/xml/schematron" name="bar">
<rule context="foo">
<assert test="count(bar|@bar)=1">Either the element bar or
the attribute bar should be specified.</assert>
</rule>
</pattern>
</xs:appinfo>
</xs:annotation>
</xs:element>
<xs:element name="bar" type="xs:anyURI"/>
<xs:complexType name="foo">
<xs:sequence>
<xs:element minOccurs="0" ref="bar"/>
</xs:sequence>
<xs:attribute name="bar" default="" type="xs:anyURI"/>
</xs:complexType>
</xs:schema>

On a document like:

<foo bar="sample">
<bar>sample</bar>
</foo>

The following error will appear:

SystemID: C:\george\workspace\oXygen\samples\test.xml
Location: 1:0
Description: Either the element bar or the attribute bar should be
specified. (count(bar|@bar)=1)

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com

[Stan Kitsis [MSFT]]

In general, this type of constraint is not available in the Xml Schema.
However, if "bar" is a simple type or a simple content element, your
particular case can be solved with the following XSD:

<xs:element name="top">

<xs:complexType>

<xs:sequence>

<xs:element name="bar" minOccurs="0" type="xs:string"/>

</xs:sequence>

<xs:attribute name="bar" type="xs:anyURI"/>

</xs:complexType>

<xs:unique name="elementORattr">

<xs:selector xpath="."/>

<xs:field xpath="tns:bar|@bar"/>

</xs:unique>

</xs:element>
I used "tns" as the namespace in the xs:field. You'll need to change it to
the prefix you've defined for the target namespace.

--
Stan Kitsis
Program Manager, XML Technologies
Microsoft Corporation

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Is it possibly to specify that I want a either a element or an
attribute to occur, but not both at the same time?

<xs:complexType name="foo">
<xs:sequence>
<xs:element minOccurs="0" ref="bar"/>
</xs:sequence>
<xs:attribute name="bar" default="" type="xs:anyURI"/>
</xs:complexType>

In this complexType I don't want both the element "bar" and the
attribute "bar" to be present, only one of them. Can I express this in
any way in xsd?

-Gisle-