XML Schema: JAXB validation for 2 attributes

[Sverre Moe]

I'm building a XML Schema to be used with JAXB and are faced with a problem with the schema.

Take the myElementType for example. It has two attributes that are requeired, but not both of them. Either of them is required if the other is omitted.
<xs:complexType name="myElementType"> <xs:sequence> <xs:element type="otherType" name="other" minOccurs="0" /> </xs:sequence> <xs:attribute type="xs:string" name="class" use="required" /> <xs:attribute type="xs:string" name="url" use="required" /> <xs:attribute type="xs:string" name="something1" use="optional" /> <xs:attribute type="xs:string" name="something2" use="optional" /> </xs:complexType>

<myelement class="clazz"> </myelement> <myelement url="http://"> </myelement>

In order for JAXB to validate this properly how can I arrange the XML Schema for this element for these 2 attributes?
I guess one of the two must have precedence over the other. If class is defined, the presence of url is invalid or vice versa.
If neither is defined it must validate that it must have either class or url.


For what I have read it seems like it is not possible to have attributes like a choice.
http://stackoverflow.com/questions/763072/xsd-one-of-2-attributes-is-required