Recursion in XML Schema

Hi:I am defining an XML schema for predicate properties. In the process, I 
have defined a global element and a global complex type associated with it. 
Now, can this complex type be referenced inside another element which is of 
this complex type itself? Here is an example:
<property> := <invariant>|<next>|<stable>
<invariant> := <predicate>|<quantification>|<property>
See how <property> has <invariant> as a child and <invariant> in turn has 
<property> as it's possible child. Is this valid?!? Will instance documents 
be valid if such recusrsion of elements occurs? Please help. Thanks
--Karuna

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