A Tractable Subclass of DTDs for XPath Satisfiability with Sibling Axes

* Final gross prices may vary according to local VAT.

Get Access


The paper presents a tractable subclass of DTDs, called DC-DTDs, for XPath satisfiability with sibling axes. A DC-DTD is a DTD such that each content model is in the form of a concatenation of single tag names and Kleene-starred regular expressions. DC-DTDs are a proper subclass of covering DTDs proposed by Montazerian et al., and a proper superclass of disjunction-free DTDs. In this paper, it is shown that tractability by covering DTDs is fragile against sibling axes. Then, tractability of XPath satisfiability with sibling axes under DC-DTDs is demonstrated. Finally, as a limitation of the tractability of DC-DTDs, it is shown that upward axes appearing in qualifiers bring intractability under even disjunction-free DTDs.