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The tree of knowledge in action: Towards a common perspective
 In G. Governatori, I. Hodkinson, & Y. Venema (Eds.), Proceedings of advances in modal logic
, 2006
"... abstract. We survey a number of decidablity and undecidablity results concerning epistemic temporal logic. The goal is to provide a general picture which will facilitate the ‘sharing of ideas ’ from a number of different areas concerned with modeling agents in interactive social situations. ..."
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Cited by 17 (7 self)
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abstract. We survey a number of decidablity and undecidablity results concerning epistemic temporal logic. The goal is to provide a general picture which will facilitate the ‘sharing of ideas ’ from a number of different areas concerned with modeling agents in interactive social situations.
The semijoin algebra and the guarded fragment
 J. Logic Lang. Inform
, 2005
"... The semijoin algebra is the variant of the relational algebra obtained by replacing the join operator by the semijoin operator. We discuss some interesting connections between the semijoin algebra and the guarded fragment of firstorder logic. We also provide an EhrenfeuchtFraïssé game, characteriz ..."
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Cited by 4 (0 self)
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The semijoin algebra is the variant of the relational algebra obtained by replacing the join operator by the semijoin operator. We discuss some interesting connections between the semijoin algebra and the guarded fragment of firstorder logic. We also provide an EhrenfeuchtFraïssé game, characterizing the discerning power of the semijoin algebra. This game gives a method for showing that certain queries are not expressible in the semijoin algebra. 1
CONJUNCTIVE QUERY ANSWERING IN THE DESCRIPTION LOGIC SH USING KNOTS
, 2009
"... Answering conjunctive queries (CQs) has been recognized as an important task for the widening use of Description Logics (DLs) in a number of applications. The problem has been studied by many authors, who developed a number of different techniques for its solution. We present a novel method for CQ a ..."
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Cited by 2 (1 self)
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Answering conjunctive queries (CQs) has been recognized as an important task for the widening use of Description Logics (DLs) in a number of applications. The problem has been studied by many authors, who developed a number of different techniques for its solution. We present a novel method for CQ answering based on knots, which are schematic subtrees of depth at most one. The method yields an algorithm for CQ answering in the DL SH which handles CQs with distinguished (i.e., output) variables in a direct manner. It proceeds by first compiling the knowledge base into a set of knots, and then constructing a set of simple knowledge bases, which contain only assertional data, over which a given query is answered. Notably, the knot compilation can be reused for varying queries and is amenable to an implementation in disjunctive Datalog. The algorithm works in double exponential time in general but in single exponential time under various restrictions on the occurrence of transitive roles in queries, including CQ answering in the DL ALCH. The results are worstcase optimal, given that CQ answering is 2EXPTIMEcomplete for SH and EXPTIMEhard already for the core expressive DL ALC. In particular, the result for ALCH reconfirms Lutz’s result that adding inverse roles to ALC causes an exponential jump in complexity, while adding role hierarchies does not. Furthermore, a nondeterministic version of our
Relativized Action Complement for Dynamic Logics
"... This paper gives motivations, de nitions and some initial results ..."
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Cited by 1 (0 self)
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This paper gives motivations, de nitions and some initial results
Bisimulation
"... s 0 t 0 there is a t 2 W such that Rst and tZt 0 . If there is some bisimulation Z linking s and s 0 then we say that s and s 0 are bisimilar, notation: s $ s 0 , or M; s $ M 0 ; s 0 if we wish to make the models explicit. Figure 1 contains two simple examples of bisimulating models ..."
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s 0 t 0 there is a t 2 W such that Rst and tZt 0 . If there is some bisimulation Z linking s and s 0 then we say that s and s 0 are bisimilar, notation: s $ s 0 , or M; s $ M 0 ; s 0 if we wish to make the models explicit. Figure 1 contains two simple examples of bisimulating models (the models bisimulate horizontally) in a language with only one unary relation P . Figure 2 shows two models which do not bisimulate at the roots; all states in both models satisfy the same unary relations; M 0 has all of the nite branches that M has, but in addition it contains an innite branch. p p s w 0 s<F11.