ELP: Tractable Rules for OWL 2

We introduce $\text{\sf{ELP}}$ as a decidable fragment of the Semantic Web Rule Language (SWRL) that admits reasoning in polynomial time. $\text{\sf{ELP}}$ is based on the tractable description logic $\mathcal{EL}^{\mathord{+}\mathord{+}}$, and encompasses an extended notion of the recently proposed DL rules for that logic. Thus $\text{\sf{ELP}}$ extends $\mathcal{EL}^{\mathord{+}\mathord{+}}$ with a number of features introduced by the forthcoming OWL 2, such as disjoint roles, local reflexivity, certain range restrictions, and the universal role. We present a reasoning algorithm based on a translation of $\text{\sf{ELP}}$ to Datalog, and this translation also enables the seamless integration of DL-safe rules into $\text{\sf{ELP}}$. While reasoning with DL-safe rules as such is already highly intractable, we show that DL-safe rules based on the Description Logic Programming (DLP) fragment of OWL 2 can be admitted in $\text{\sf{ELP}}$ without losing tractability.