We consider the navigational core of XPath, extended with two operators: the Kleene star for taking the transitive closure of path expressions, and a subtree relativisation operat...
We give two sufficient conditions on XPath like languages for having first order expressivity, meaning that every first order definable set of paths in an ordered node-labeled t...
ct The backbone of the XML data model, namely ordered, unranked trees, is inherently recursive and it is natural to equip the associated languages with constructs that can query su...