All-Instances Restricted Chase Termination for Linear TGDs

Abstract

The chase procedure is a fundamental algorithmic tool in database theory with a variety of applications. A key problem concerning the chase procedure is all-instances chase termination: for a given set of tuple-generating dependencies (TGDs), is it the case that the chase terminates for every input database? In view of the fact that this problem is, in general, undecidable, it is natural to ask whether well-behaved classes of TGDs, introduced in different contexts, ensure decidability. It has been recently shown that the problem is decidable for the restricted (a.k.a. standard) version of the chase, and linear TGDs, a prominent class of TGDs that has been introduced in the context of ontological query answering, under the assumption that only one atom appears in TGD-heads. We provide an alternative proof for this result based on Monadic Second-Order Logic, which we believe is simpler that the ones obtained from the literature.

Non-Uniformly Terminating Chase: Size and Complexity

“…There are also recent results for sticky TGDs (another well-behaved class that is inherently unguarded), and the semi-oblivious version of the chase [9]. The restricted chase has been recently studied with linear TGDs [17,22], as well as with guarded and sticky TGDs [16].…”