Is PL2 a Tractable Language?
نویسندگان
چکیده
It is believed by the scientific community that PL1 and PL2 are the largest concept languages for which there exists a polynomial algorithm that solves the subsumption problem. This is due to Donini, Lenzerini, Nardi, and Nutt, who have presented two tractable algorithms that are intended to solve the subsumption problem in those languages. In contrast, this paper proves that the algorithm for checking subsumption of concepts expressed in the language PL2 is not complete. As a direct consequence, it still remains an open problem to which computational complexity class this subsumption problem belongs.
منابع مشابه
Tractable Concept Languages
Abst rac t We present two concept languages,, called PL1 and PL2 which are extensions of TC. We prove that the subsumption problem in these languages can be solved in polynomial time. Both languages include a construct for expressing inverse roles, which has not been considered up to now in tractable languages. In addition, PL1 includes number restrictions and negation of primitive concepts, wh...
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