Results 1  10
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159
RealTime Systems
, 2000
"... Collision avoidance is an important topic in multirobot systems. Existing multirobot pathfinding approaches ignore sideswipe collisions among robots (i.e., only consider the collision which two agents try to occupy the same node during the same timestep) [1, 3, 4], and allow diagonal move between ..."
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Cited by 425 (9 self)
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Collision avoidance is an important topic in multirobot systems. Existing multirobot pathfinding approaches ignore sideswipe collisions among robots (i.e., only consider the collision which two agents try to occupy the same node during the same timestep) [1, 3, 4], and allow diagonal move between two adjacent nodes (e.g., Figure 1(b)). However, in many real world applications, sideswipe collisions may also block robots ’ movements or cause deadlocks. For example, as shown in Figure 1, if the size of two robots is as big as the grid size they occupied, collisions will happen not only between robots R1 and R2 in the situation depicted in Figure 1(a), but also that in Figure 1(b), which is typically not considered as a collision in existing multirobot systems. (a) (b) (c) Figure 2: Illustration of deadloop. The green square and the red square are the robot positions and the goal positions for two robots, respectively. R1 and R2 are robot 1 and robot 2. (a) The initial position for two robots. (b) and (c) The dead looping condition is encountered and repeated inbetween (b) and (c) infinitely as each robot makes a move that mirrors the other robot’s.
Description Logic Programs: Combining Logic Programs with Description Logic
, 2003
"... We show how to interoperate, semantically and inferentially, between the leading Semantic Web approaches to rules (RuleML Logic Programs) and ontologies (OWL/DAML+OIL Description Logic) via analyzing their expressive intersection. To do so, we define a new intermediate knowledge representation (KR) ..."
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Cited by 397 (41 self)
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We show how to interoperate, semantically and inferentially, between the leading Semantic Web approaches to rules (RuleML Logic Programs) and ontologies (OWL/DAML+OIL Description Logic) via analyzing their expressive intersection. To do so, we define a new intermediate knowledge representation (KR) contained within this intersection: Description Logic Programs (DLP), and the closely related Description Horn Logic (DHL) which is an expressive fragment of firstorder logic (FOL). DLP provides a significant degree of expressiveness, substantially greater than the RDFSchema fragment of Description Logic.
Tabled Evaluation with Delaying for General Logic Programs
, 1996
"... SLD resolution with negation as finite failure (SLDNF) reflects the procedural interpretation of predicate calculus as a programming language and forms the computational basis for Prolog systems. Despite its advantages for stackbased memory management, SLDNF is often not appropriate for query evalu ..."
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Cited by 260 (27 self)
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SLD resolution with negation as finite failure (SLDNF) reflects the procedural interpretation of predicate calculus as a programming language and forms the computational basis for Prolog systems. Despite its advantages for stackbased memory management, SLDNF is often not appropriate for query evaluation for three reasons: a) it may not terminate due to infinite positive recursion; b) it may not terminate due to infinite recursion through negation; c) it may repeatedly evaluate the same literal in a rule body, leading to unacceptable performance. We address three problems fir a goaloriented query evaluation of general logic programs by presenting tabled evaluation with delaying (SLG resolution).
Supporting Structured Credentials and Sensitive Policies through Interoperable Strategies for Automated Trust Negotiation
 ACM TRANSACTIONS ON INFORMATION AND SYSTEM SECURITY
, 2003
"... ... this paper we provide the formal underpinnings for that goal, by formalizing the concepts of negotiation protocols, strategies, and interoperation. We show how to model the information flow of a negotiation, for use in analyzing strategy interoperation. We also present two large sets of strategi ..."
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Cited by 136 (19 self)
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... this paper we provide the formal underpinnings for that goal, by formalizing the concepts of negotiation protocols, strategies, and interoperation. We show how to model the information flow of a negotiation, for use in analyzing strategy interoperation. We also present two large sets of strategies whose members all interoperate with one another, and show that these sets contain many practical strategies. We develop the theory both for blackbox propositional credentials and credentials with internal structure, and for access control policies whose contents are (resp. are not) sensitive. We also discuss how these results fit into TrustBuilder, our prototype system for trust negotiation
A Portrait of the Semantic Web in Action
 IEEE Intelligent Systems
"... The Web’s phenomenal growth rate makes it increasingly difficult to locate, organize, and integrate the available information. To cope with the enormous quantity of data, we need to hand off portions of these tasks to machines. However, because naturallanguage processing is still an unsolved proble ..."
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Cited by 98 (1 self)
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The Web’s phenomenal growth rate makes it increasingly difficult to locate, organize, and integrate the available information. To cope with the enormous quantity of data, we need to hand off portions of these tasks to machines. However, because naturallanguage processing is still an unsolved problem, machines cannot understand Without semantically enriched content, the Web cannot reach its full potential. The authors discuss tools and techniques for generating and processing such content, thus setting a foundation upon which to build the Semantic Web. the Web pages to the extent required to perform the desired tasks. An alternative is to change the Web to make it more understandable by machines, thereby creating a Semantic Web. Many researchers believe the key to building this new Web lies in the development of semantically enriched languages. Early languages,
Parameter learning of logic programs for symbolicstatistical modeling
 Journal of Artificial Intelligence Research
, 2001
"... We propose a logical/mathematical framework for statistical parameter learning of parameterized logic programs, i.e. de nite clause programs containing probabilistic facts with a parameterized distribution. It extends the traditional least Herbrand model semantics in logic programming to distributio ..."
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Cited by 92 (19 self)
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We propose a logical/mathematical framework for statistical parameter learning of parameterized logic programs, i.e. de nite clause programs containing probabilistic facts with a parameterized distribution. It extends the traditional least Herbrand model semantics in logic programming to distribution semantics, possible world semantics with a probability distribution which is unconditionally applicable to arbitrary logic programs including ones for HMMs, PCFGs and Bayesian networks. We also propose a new EM algorithm, the graphical EM algorithm, thatrunsfora class of parameterized logic programs representing sequential decision processes where each decision is exclusive and independent. It runs on a new data structure called support graphs describing the logical relationship between observations and their explanations, and learns parameters by computing inside and outside probability generalized for logic programs. The complexity analysis shows that when combined with OLDT search for all explanations for observations, the graphical EM algorithm, despite its generality, has the same time complexity as existing EM algorithms, i.e. the BaumWelch algorithm for HMMs, the InsideOutside algorithm for PCFGs, and the one for singly connected Bayesian networks that have beendeveloped independently in each research eld. Learning experiments with PCFGs using two corpora of moderate size indicate that the graphical EM algorithm can signi cantly outperform the InsideOutside algorithm. 1.
ProB: A Model Checker for B
 FME 2003: FORMAL METHODS, LNCS 2805
, 2003
"... We present ProB, an animation and model checking tool for the B method. ProB's animation facilities allow users to gain confidence in their specifications, and unlike the animator provided by the BToolkit, the user does not have to guess the right values for the operation arguments or choice va ..."
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Cited by 84 (28 self)
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We present ProB, an animation and model checking tool for the B method. ProB's animation facilities allow users to gain confidence in their specifications, and unlike the animator provided by the BToolkit, the user does not have to guess the right values for the operation arguments or choice variables. ProB contains a model checker and a constraintbased checker, both of which can be used to detect various errors in B specifications. We present our first experiences in using ProB on several case studies, highlighting that ProB enables users to uncover errors that are not easily discovered by existing tools.
Efficient TopDown Computation of Queries under the WellFounded Semantics
 JOURNAL OF LOGIC PROGRAMMING
, 1994
"... The wellfounded model provides a natural and robust semantics for logic programs with negative literals in rule bodies. Although various procedural semantics have been proposed for query evaluation under the wellfounded semantics, the practical issues of implementation for effective and efficient ..."
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Cited by 81 (12 self)
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The wellfounded model provides a natural and robust semantics for logic programs with negative literals in rule bodies. Although various procedural semantics have been proposed for query evaluation under the wellfounded semantics, the practical issues of implementation for effective and efficient computation of queries have been rarely discussed. This paper investigates two major implementation issues of query evaluation under the wellfounded semantics, namely (a) to ensure that negative literals be resolved only after their positive counterparts have been completely evaluated, and (b) to detect and handle potential negative loops. We present efficient incremental algorithms for maintaining positive and negative dependencies among subgoals in a topdown evaluation. Both completely evaluated subgoals and potential negative loops are detected by inspecting the dependency information of a single subgoal. Our implementation can be viewed as an effective successor to SLDNF resolution, ex...
Research Agenda for the Semantic Grid: A Future eScience Infrastructure
, 2001
"... for comment with limited circulation to the UK Research Councils eScience ..."
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Cited by 56 (7 self)
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for comment with limited circulation to the UK Research Councils eScience
Infinite state model checking by abstract interpretation and program specialisation
 LogicBased Program Synthesis and Transformation. Proceedings of LOPSTR’99, LNCS 1817
, 2000
"... Abstract. We illustrate the use of logic programming techniques for finite model checking of CTL formulae. We present a technique for infinite state model checking of safety properties based upon logic program specialisation and analysis techniques. The power of the approach is illustrated on severa ..."
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Cited by 55 (24 self)
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Abstract. We illustrate the use of logic programming techniques for finite model checking of CTL formulae. We present a technique for infinite state model checking of safety properties based upon logic program specialisation and analysis techniques. The power of the approach is illustrated on several examples. For that, the efficient tools logen and ecce are used. We discuss how this approach has to be extended to handle more complicated infinite state systems and to handle arbitrary CTL formulae. 1