On Core XPath with Inflationary Fixed Points
We prove the undecidability of Core XPath 1.0 (CXP) [G. Gottlob and C. Koch, in IEEE CS Press (2002) 189–202.] extended with an operator. More specifically, we prove that the satisfiability problem of this language is undecidable. In fact, the fragment of CXP+IFP containing only the and axes is already undecidable.