>2. Adding a separate construct to XACML policy schema to represent >sequences of attribute values, such that you cannot create sequeences of >sequences. As an alternative to my proposal to modify schema element <attributevalue>, I propose to define standard core function collection <type>-sequence of undefined arity, that takes arguments of singleton <type> kind and return a sequence<type> value, a sequence of its argument values. In this case, when a literal sequence definition is needed, this funciton can be used. No schema modification is needed. The drawback is that it can not be used to specify an argument of sequence<type> kind for predicate functions that can be used in <Match> elements. Daniel.