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Michael Thielscher - One of the best experts on this subject based on the ideXlab platform.
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Artificial Intelligence 111(1–2): 277–299 (1999). From Situation Calculus to Fluent Calculus: State Update Axioms as a Solution to the Inferential Frame Problem
2015Co-Authors: Michael ThielscherAbstract:Abstract. Successor state axioms provide a solution to the famous Frame Problem as far as the representational aspect is concerned. Solving in classical, monotonic logic the additional inferential Frame Problem, on the other hand, was the major motivation for the development of the Fluent Calculus a decade or so ago. Yet the expressiveness of the latter in comparison to the Situation Calculus remained a largely open question until today. In this note, we derive a novel version of the Fluent Calculus by gradually applying the principle of reification to successor state axioms in order to address the inferential Frame Problem without losing the representational merits. Our approach results in a fully mechanic method for the generation of state update axioms from any collection of Situation Calculus-style effect axioms for deterministic actions, provided the actions do not have potentially infinitely many effects. The axiomatization thus obtained is proved essentially equivalent to the corresponding axiomatization which uses successor state axioms
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1The Concurrent, Continuous Fluent Calcu- lus
2015Co-Authors: Michael ThielscherAbstract:Abstract. The Fluent Calculus belongs to the established predicate cal-culus formalisms for reasoning about actions. Its underlying concept of state update axioms provides a solution to the basic representational and inferen-tial Frame Problems in pure first-order logic. Extending a recent research result, we present a Fluent Calculus to reason about domains involving con-tinuous change and where actions occur concurrently. Research into Cognitive Robotics aims at explaining and modeling intelli-gent acting in a dynamic world. Whenever intelligent behavior is understood as resulting from correct reasoning on correct representations, the classical Frame Problem [6] is a fundamental theoretical challenge: Given a represen
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The Qualification Problem: A solution to the problem of anomalous models
2015Co-Authors: Michael ThielscherAbstract:Abstract. Intelligent agents in open environments inevitably face the Quali¯cation Problem: The executability of an action can never be predicted with absolute certainty; unexpected cir-cumstances, albeit unlikely, may at any time prevent the successful performance of an action. Reasoning agents in real-world environments rely on a solution to the Quali¯cation Problem in order to make useful predictions but also to explain and recover from unexpected action failures. Yet the main theoretical result known today in this context is a negative one: While a solution to the Quali¯cation Problem requires to assume away by default abnormal quali¯cations of actions, straightforward minimization of abnormality falls prey to the production of anomalous models. We present an approach to the Quali¯cation Problem which resolves this anomaly. Anomalous models are shown to arise from ignoring causality, and they are avoided by appealing to just this concept. Our theory builds on the established predicate logic formalism of the Fluent Cal-culus as a solution to the Frame Problem and to the Rami¯cation Problem in reasoning about actions. The monotonic Fluent Calculus is enhanced by a default theory in order to obtain the nonmonotonic approach called for by the Quali¯cation Problem. The approach has been implemented in an action programming language based on the Fluent Calculus and successfully applied to the high-level control of robots
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A Unifying Action Calculus
2010Co-Authors: Michael ThielscherAbstract:Abstract McCarthy’s Situation Calculus is arguably the oldest special-purpose knowledge representa-tion formalism, designed to axiomatize knowledge of actions and their effects. Four decades of research in this area has led to a variety of alternative formalisms: While some approaches can be considered instances or extensions of the classical Situation Calculus, like Reiter’s successor state axioms or the Fluent Calculus, there also exist special planning languages like ADL and approaches based on a linear (rather than branching) time structure like the Event Calculus. The co-existence of many different cal-culi has two main disadvantages: The formal relations among them is a largely open issue, and a lot of today’s research concerns the transfer of specific results obtained for one approach to another one. In this paper, we present a unifying action Calculus, of which we show that it encompasses (well-defined classes of) all of the aforementioned formalisms. Our Calculus not only facilitates comparisons and translations between specific approaches, it also allows to solve interesting problems for various calculi at once. We exemplify this by providing a general, Calculus-independent solution to a problem of practical relevance: the modularity of domain axiomatizations.
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a Fluent Calculus semantics for adl with plan constraints
European Conference on Logics in Artificial Intelligence, 2008Co-Authors: Conrad Drescher, Michael ThielscherAbstract:Plan constraints are the most recent addition to the ever growing Planning Domain Definition Language (PDDL). In this work we consider the PDDL fragment consisting of basic ADL extended by plan constraints. We provide a purely declarative semantics for this fragment by interpreting it in the basic Fluent Calculus. We thus obtain a logical semantics for this fragment of PDDL instead of the usual meta-theoretical state transition semantics.
Hans-peter Storr - One of the best experts on this subject based on the ideXlab platform.
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Reasoning about Complex Actions
2007Co-Authors: Steffen Holldobler, Hans-peter StorrAbstract:Many problems addressed within the field of Cognitive Robotics and related areas can only be solved by complex plans including conditional and recursive actions as well as non-deterministic choice operators. In this paper we present a planning language which allows for the specication of complex plans. We define its semantics and give a provably complete and correct completed equational logic program with an unification complete equational theory. The approach is independent of the representation of states; they may be sets of propositional Fluents as in the situation Calculus or multisets of resources as in the Fluent Calculus. Finally, we give an instantiation within the Fluent Calculus
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Solving the Entailment Problem in the Fluent Calculus using Binary Decision Diagrams
2007Co-Authors: Steffen Holldobler, Hans-peter StorrAbstract:The paper is an exercise in formal program development. It is rigorously shown how planning problems encoded as entailment problems in the Fluent Calculus can be mapped onto satisfiability problems for propositional formulas, which in turn can be mapped to the problem to find models using binary decision diagrams. Preliminary experimental results of an implementation are discussed
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Planning in the Fluent Calculus Using Binary Decision Diagrams
Ai Magazine, 2001Co-Authors: Hans-peter StorrAbstract:BDDplan was created to perform certain reasoning processes in the Fluent Calculus, a flexible framework for reasoning about action and change based on first-order logic with equality (plus some second-order extensions in some cases). The reasoning is done by mapping the problems into propositional logic, which, in turn, can be implemented as operations on binary decision diagrams (BDDs).
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a new equational foundation for the Fluent Calculus
Lecture Notes in Computer Science, 2000Co-Authors: Hans-peter Storr, Michael ThielscherAbstract:A new equational foundation is presented for the Fluent Calculus, an established predicate Calculus formalism for reasoning about actions. We discuss limitations of the existing axiomatizations of both equality of states and what it means for a Fluent to hold in a state. Our new and conceptually even simpler theory is shown to overcome the restrictions of the existing approach. We prove that the correctness of the Fluent Calculus as a solution to the Frame Problem still holds under the new foundation. Furthermore, we extend our theory by an induction axiom needed for reasoning about integer-valued resources.
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solving the entailment problem in the Fluent Calculus using binary decision diagrams
Lecture Notes in Computer Science, 2000Co-Authors: Steffen Holldobler, Hans-peter StorrAbstract:It is rigorously shown how planning problems encoded as a class of entailment problems in the Fluent Calculus can be mapped onto satisfiability problems for propositional formulas, which in turn can be mapped to the problem of finding models using binary decision diagrams (BDDs). The mapping is shown to be sound and complete. First experimental results of an implementation are presented and discussed.
Steffen Holldobler - One of the best experts on this subject based on the ideXlab platform.
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Planning problems in Petri Nets and Fluent Calculus
2014Co-Authors: Ferdian Jovan, Steffen Holldobler, Bertram FronhöferAbstract:Fluent Calculus ’ and the work presented in it are my own. I confirm that: This work was done wholly or mainly while in candidature for a research degree at Technische Universität Dresden. Where any part of this thesis has previously been submitted for a degree or any other qualification at Technische Universität Dresden or any other institution, this has been clearly stated. Where I have consulted the published work of others, this is always clearly attributed. Where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work. I have acknowledged all main sources of help. Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself
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Descriptions in the Fluent Calculus
2007Co-Authors: Steffen HolldoblerAbstract:An attempt to combine reasoning about actions in the uent Calculus with description logics is described. It extends description logics in that concepts may be situation{dependent. In particular, an object may belong to a dierent concept before and after the execution of an action. It extends the uent Calculus by inheritance and overriding of action descriptions and, in particular, it generalizes the work reported in [5]. Keywords: Knowledge Representation, Reasoning about Actions, Fluent Calculus, Description Logics, Specicity. 1 Introduction In almost all applications of logic based approaches to reasoning about actions the underlying domain is at and unstructured (see e.g. [7]). Concepts, hierarchies and taxonomies are usually not specied or used in the denition of actions. Inheritance does not play a role in many formalisms for reasoning about actions, although this is known to be a quite powerful technique. In particular | and this is a major drawback of current proposals..
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Solving the Entailment Problem in the Fluent Calculus using Binary Decision Diagrams
2007Co-Authors: Steffen Holldobler, Hans-peter StorrAbstract:The paper is an exercise in formal program development. It is rigorously shown how planning problems encoded as entailment problems in the Fluent Calculus can be mapped onto satisfiability problems for propositional formulas, which in turn can be mapped to the problem to find models using binary decision diagrams. Preliminary experimental results of an implementation are discussed
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Reasoning about Complex Actions
2007Co-Authors: Steffen Holldobler, Hans-peter StorrAbstract:Many problems addressed within the field of Cognitive Robotics and related areas can only be solved by complex plans including conditional and recursive actions as well as non-deterministic choice operators. In this paper we present a planning language which allows for the specication of complex plans. We define its semantics and give a provably complete and correct completed equational logic program with an unification complete equational theory. The approach is independent of the representation of states; they may be sets of propositional Fluents as in the situation Calculus or multisets of resources as in the Fluent Calculus. Finally, we give an instantiation within the Fluent Calculus
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A logic-based approach to dynamic programming
AAAI Press, 2004Co-Authors: Steffen Holldobler, Olga Skvortsova, Technische Universität DresdenAbstract:We present a first-order value iteration algorithm that addresses the scalability problem of classical dynamic programming techniques by logically partitioning the state space. An MDP is represented in the Probabilistic Fluent Calculus, that is a first-order language for reasoning about actions. Moreover, we develop a normalization algorithm that discovers and prunes redundant states. We have implemented our approach and describe some experimental results
Dimitris Plexousakis - One of the best experts on this subject based on the ideXlab platform.
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A specification-based QoS-aware design framework for service-based applications
Service Oriented Computing and Applications, 2017Co-Authors: George Baryannis, Kyriakos Kritikos, Dimitris PlexousakisAbstract:Effective and accurate service discovery and composition rely on complete specifications of service behaviour, containing inputs and preconditions that are required before service execution, outputs, effects and ramifications of a successful execution and explanations for unsuccessful executions. The previously defined Web Service Specification Language (WSSL) relies on the Fluent Calculus formalism to produce such rich specifications for atomic and composite services. In this work, we propose further extensions that focus on the specification of QoS profiles, as well as partially observable service states. Additionally, a design framework for service-based applications is implemented based on WSSL, advancing state of the art by being the first service framework to simultaneously provide several desirable capabilities, such as supporting ramifications and partial observability, as well as non-determinism in composition schemas using heuristic encodings; providing explanations for unexpected behaviour; and QoS-awareness through goal-based techniques. These capabilities are illustrated through a comparative evaluation against prominent state-of-the-art approaches based on a typical SBA design scenario.
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Fluent Calculus based semantic web service composition and verification using wssl
International Conference on Service Oriented Computing, 2013Co-Authors: George Baryannis, Dimitris PlexousakisAbstract:We propose a composition and verification framework for Semantic Web Services specified using WSSL, a novel service specification language based on the Fluent Calculus, that addresses issues related to the frame, ramification and qualification problems. These deal with the succinct and flexible representation of non-effects, indirect effects and preconditions, respectively. The framework exploits the unique features of WSSL, allowing, among others, for: compositions that take into account ramifications of services; determining the feasibility of a composition a priori; and considering exogenous qualifications during the verification process. The framework is implemented using FLUX-based planning, supporting compositions with fundamental control constructs, including nondeterministic ones such as conditionals and loops. Performance is evaluated with regard to termination and execution time for increasingly complex synthetic compositions.
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wssl a Fluent Calculus based language for web service specifications
Conference on Advanced Information Systems Engineering, 2013Co-Authors: George Baryannis, Dimitris PlexousakisAbstract:In order to effectively discover and invoke a Web service, the provider must supply a complete specification of its behavior, with regard to its inputs, outputs, preconditions and effects. Devising such complete specifications comes with many issues that have not been adequately addressed by current service description efforts, such as WSDL, SAWSDL, OWL-S and WSMO. These issues involve the frame, ramification and qualification problems, which deal with the succinct and flexible representation of non-effects, indirect effects and preconditions, respectively. We propose WSSL, a novel specification language for services, based on the Fluent Calculus, that is expressly designed to address the aforementioned issues. Also, a tool is implemented that translates WSSL specifications to FLUX programs and allows for service validation based on user-defined goals.
George Baryannis - One of the best experts on this subject based on the ideXlab platform.
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A specification-based QoS-aware design framework for service-based applications
Service Oriented Computing and Applications, 2017Co-Authors: George Baryannis, Kyriakos Kritikos, Dimitris PlexousakisAbstract:Effective and accurate service discovery and composition rely on complete specifications of service behaviour, containing inputs and preconditions that are required before service execution, outputs, effects and ramifications of a successful execution and explanations for unsuccessful executions. The previously defined Web Service Specification Language (WSSL) relies on the Fluent Calculus formalism to produce such rich specifications for atomic and composite services. In this work, we propose further extensions that focus on the specification of QoS profiles, as well as partially observable service states. Additionally, a design framework for service-based applications is implemented based on WSSL, advancing state of the art by being the first service framework to simultaneously provide several desirable capabilities, such as supporting ramifications and partial observability, as well as non-determinism in composition schemas using heuristic encodings; providing explanations for unexpected behaviour; and QoS-awareness through goal-based techniques. These capabilities are illustrated through a comparative evaluation against prominent state-of-the-art approaches based on a typical SBA design scenario.
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Fluent Calculus based semantic web service composition and verification using wssl
International Conference on Service Oriented Computing, 2013Co-Authors: George Baryannis, Dimitris PlexousakisAbstract:We propose a composition and verification framework for Semantic Web Services specified using WSSL, a novel service specification language based on the Fluent Calculus, that addresses issues related to the frame, ramification and qualification problems. These deal with the succinct and flexible representation of non-effects, indirect effects and preconditions, respectively. The framework exploits the unique features of WSSL, allowing, among others, for: compositions that take into account ramifications of services; determining the feasibility of a composition a priori; and considering exogenous qualifications during the verification process. The framework is implemented using FLUX-based planning, supporting compositions with fundamental control constructs, including nondeterministic ones such as conditionals and loops. Performance is evaluated with regard to termination and execution time for increasingly complex synthetic compositions.
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wssl a Fluent Calculus based language for web service specifications
Conference on Advanced Information Systems Engineering, 2013Co-Authors: George Baryannis, Dimitris PlexousakisAbstract:In order to effectively discover and invoke a Web service, the provider must supply a complete specification of its behavior, with regard to its inputs, outputs, preconditions and effects. Devising such complete specifications comes with many issues that have not been adequately addressed by current service description efforts, such as WSDL, SAWSDL, OWL-S and WSMO. These issues involve the frame, ramification and qualification problems, which deal with the succinct and flexible representation of non-effects, indirect effects and preconditions, respectively. We propose WSSL, a novel specification language for services, based on the Fluent Calculus, that is expressly designed to address the aforementioned issues. Also, a tool is implemented that translates WSSL specifications to FLUX programs and allows for service validation based on user-defined goals.