Abstract. We consider the setting of ontological database access, where an Abox is given in form of a relational database D and where a Boolean conjunctive query q has to be evaluated against D modulo a T -box Σ formulated in DLLite or Linear Datalog ± . It is well-known that (Σ, q) can be rewritten into an equivalent nonrecursive Datalog program P that can be directly evaluated over D. However, for Linear Datalog ± or for DL-Lite versions that allow for role inclusion, the rewriting methods described so far result in a nonrecursive Datalog program P of size exponential in the joint size of Σ and q. This gives rise to the interesting question of whether such a rewriting necessarily needs to be of exponential size. In this paper we show that it is actually possible to translate (Σ, q) into a polynomially sized equivalent nonrecursive Datalog program P .
For DL-Lite R , the authors in REF propose a rewriting into a polynomially-sized non-recursive DATALOG program, assuming that the data contains some fixed number of constants.
Rewriting Ontological Queries into Small Nonrecursive Datalog Programs
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Computer Science