an Schema for this xml?

Hello,

Please i can't resolve a XML-Schema for the following xml:

<mycontainer>
	<myelement name="n1" a="0" b="1">
		<mynestedelement c="2"/>
	</myelement>
	<myelement name="n2" a="0" b="1">
		<mynestedelement c="2"/>
	</myelement>
	<myelement href="doc2.xml" path="mycontainer/myelement#n3"/>
</mycontainer>


where attributes name, a and b are required and mynestedelement is also required.

at the other side, attributes href and path are required, and is simpleContent

how can write an schema where an element has two ways of be described?

thanks in advance
May, DrMay