The pre-defined rule-sets are layered such that each one extends the preceding one. The following list is ordered by increasing expressivity:
empty
: no reasoning, i.e. OWLIM operates as a plain RDF store;rdfs
: supports standard RDFS semantics;owl-horst
: OWL dialect close to OWL Horst; the differences are discussed below;owl-max
: a combination of most of OWL-Lite with RDFS.Furthermore, the OWL2 RL profile [5], is supported as follows:
owl2-rl-conf
: Fully conformant except for D-Entailment, i.e. reasoning about data types;owl2-rl-reduced
: As above, but with the troublesome prp-key rule removed (this rule causes serious scalability problems).OWLIM has an internal rule compiler that can be used to configure the TRREE with a custom set of inference rules and axioms. The user may define a custom rule-set in a *.pie file (e.g. MySemantics.pie). The easiest way to do this is to start modifying one of the .pie files that were used to build the pre-compiled rule-sets all pre-defined .pie files are included in the distribution. The syntax of the .pie files is easy to follow.
OWL compliance, OWLIM supports several OWL like dialects: OWL Horst [4], (owl-horst
), OWL Max (owl-max
) that covers most of OWL-Lite and RDFS, and OWL2 RL (owl2-rl-conf
and owl2-rl- reduced
).
With the owl-max
rule-set, which is is represented in Figure 3, OWLIM supports the following semantics:
The differences between OWL Horst [4], and the OWL dialects supported by OWLIM (owl-horst
and owl-max
) can be summarized as follows:
owl-max
). These are listed in the OWLIM user guides;Even though the concrete rules pre-defined in OWLIM differ from those defined in OWL Horst, the complexity and decidability results reported for R-entailment are relevant for TRREE and OWLIM. To put it more precisely, the rules in the owl-host
rule-set do not introduce new B-Nodes, which means that R-entailment with respect to them takes polynomial time. In KR terms, this means that the owl-horst
inference within OWLIM is tractable.
Inference using owl-horst
is of a lesser complexity compared to other formalisms that combine DL formalisms with rules. In addition, it puts no constraints with respect to meta-modeling.
The correctness of the support for OWL semantics (for those primitives that are supported) is checked against the normative Positive- and Negative-entailment OWL test cases [6]. These tests are provided in the OWLIM distribution and documented in the OWLIM user guides.
Figure 3 - Owl-max and Other OWL Dialects