Forced enumeration of elements using schemas

[cholas]

Hi all,

I've got a list of assets, and each asset is available in different languages. My XML structure describing this looks something like:

<asset type="audio" id="asset001">
<resource language="English" source="asset001eng.mp3"/>
<resource language="French" source="asset001fre.mp3"/>
</asset>

Is it possible, using schemas, to inisist on one resource element appearing once per defined language, and that each resource element must have a different language type, and if so how do I go about achieveing this?

Thanks in advance

Nick