context IEXUAAssertionSpec
inv: self.attributeStatement->size() > 0 and
self.attributeStatement->forAll(ast : AttributeStatementType | 
	ast.attribute->size() > 0 and 
	ast.attribute->exists(at : AttributeType | 
		not(at.name.oclIsUndefined()) and 
		at.name ='urn:oasis:names:tc:xspa:1.0:subject:subject-id' and 
		at.attributeValue->size()>0
	)
)