active logic semantics for a single agent in a static world for some time we have been developing and have had significant practical success with a time sensitive contradiction tolerant logical reasoning engine called the active logic machine alma the current paper details a semantics for a general version of the underlying logical formalism active logic central to active logic are special rules controlling the inheritance of beliefs in general and of beliefs about the current time in particular very tight controls on what can be derived from direct contradictions email protected p and mechanisms allowing an agent to represent and reason about its own beliefs and past reasoning furthermore inspired by the notion that until an agent notices that a set of beliefs is contradictory that set seems consistent and the agent therefore reasons with it as if it were consistent we introduce an apperception function that represents an agent s limited awareness of its own beliefs and serves to modify inconsistent belief sets so as to yield consistent sets using these ideas we introduce a new definition of logical consequence in the context of active logic as well as a new definition of soundness such that when reasoning with consistent premises all classically sound rules remain sound in our new sense however not everything that is classically sound remains sound in our sense for by classical definitions all rules with contradictory premises are vacuously sound whereas in active logic not everything follows from a contradiction

a generalized time quantifier approach to approximate reasoning abstract in this paper a rather expressive fuzzy temporal logic for linear time is introduced first this logic is a multivalued generalization lukasiewicz style of a two valued linear time temporal logic based on e g the until operator second it is obtained by introducing a generalized time quantifier a generalization of the partition operator investigated by shen applied to fuzzy time sets in this fuzzy temporal logic generalized compositional rules of inference suitable for approximate reasoning in a temporal setting are presented as valid formulas some medical examples illustrate our approach

semi quantitative system identification abstract system identification takes a space of possible models and a stream of observational data of a physical system and attempts to identify the element of the model space that best describes the observed system in traditional approaches the model space is specified by a parameterized differential equation and identification selects numerical parameter values so that simulation of the model best matches the observations we present squid a method for system identification in which the space of potential models is defined by a semi quantitative differential equation sqde qualitative and monotonic function constraints as well as numerical intervals and functional envelopes bound the set of possible models the simulator sqsim predicts semi quantitative behavior descriptions from the sqde identification takes place by describing the observation stream in similar semi quantitative terms and intersecting the two descriptions to derive narrower bounds on the model space refinement is done by refuting impossible or implausible subsets of the model space squid therefore has strengths particularly robustness and expressive power for incomplete knowledge that complement the properties of traditional system identification methods we also present detailed examples evaluation and analysis of squid

on point based temporal disjointness abstract we address the problems of determining consistency and of finding a solution for sets of three point relations expressing exclusion of a point from an interval and for sets of four point relations expressing interval disjointness availability of these relations is an important requirement for dealing with the sorts of temporal constraints encountered in many ai applications such as plan reasoning we prove that consistency testing is np complete and finding a solution is np hard

on the stability of boundary conditions for molecular dynamics we study the stability of boundary conditions for molecular dynamics simulations a general stability criterion is established we first consider a one dimensional model with nearest neighbor interaction and multiple neighbor interactions we then generalize the results to more realistic models in 3d with nonlinear atomic interaction

absorbing boundary conditions for difference approximations to the multi dimensional wave equation construction des conditions aux limites absorbantes pour l equation des ondes multidimensionnelle a l aide d approximations aux differences formulation sous forme canonique des conditions aux limites absorbantes analytiques

artificial boundary conditions for the linearized benjamin bona mahony equation we consider various approximations of artificial boundary conditions for linearized benjamin bona mahoney equation continuous respectively discrete artificial boundary conditions involve non local operators in time which in turn requires to compute time convolutions and invert the laplace transform of an analytic function respectively the z transform of an holomorphic function in this paper we derive explicit transparent boundary conditions both continuous and discrete for the linearized bbm equation the equation is discretized with the crank nicolson time discretization scheme and we focus on the difference between the upwind and the centered discretization of the convection term we use these boundary conditions to compute solutions with compact support in the computational domain and also in the case of an incoming plane wave which is an exact solution of the linearized bbm equation we prove consistency stability and convergence of the numerical scheme and provide many numerical experiments to show the efficiency of our tranparent boundary conditions

an introduction to probabilistic l valued logic abstract in this paper an approach to a so called probabilistic l valued logic system constructed by the use of hirota s concept of probabilistic set is considered some basic notions of l valued logic are discussed first and after a short introduction of the concept of probabilistic set and its distribution function description the fundamental notions of probabilistic l valued logic are presented the considerations are illustrated by means of a numerical example

temporal constraint networks abstract this paper extends network based methods of constraint satisfaction to include continuous variables thus providing a framework for processing temporal constraints in this framework called temporal constraint satisfaction problem tcsp variables represent time points and temporal information is represented by a set of unary and binary constraints each specifying a set of permitted intervals the unique feature of this framework lies in permitting the processing of metric information namely assessments of time differences between events we present algorithms for performing the following reasoning tasks finding all feasible times that a given event can occur finding all possible relationships between two given events and generating one or more scenarios consistent with the information provided we distinguish between simple temporal problems stps and general temporal problems the former admitting at most one interval constraint on any pair of time points we show that the stp which subsumes the major part of vilain and kautz s point algebra can be solved in polynomial time for general tcsps we present a decomposition scheme that performs the three reasoning tasks considered and introduce a variety of techniques for improving its efficiency we also study the applicability of path consistency algorithms as preprocessing of temporal problems demonstrate their termination and bound their complexities

temporal scenario modelling and recognition based on possibilistic logic we propose in this paper a new approach for the modelling and recognition of temporal scenarios a scenario is represented by three different structures the first one models the logical dependency between the elements of the scenario using possibilistic logic while the second one is the minimal temporal graph representing all temporal constraints between the events the third structure explains the way the matching between observations and scenarios has to be done the consistency between the three structures is ensured

incremental qualitative temporal reasoning algorithms for the point algebra and the ord horn class in many applications of temporal reasoning we are interested in processing temporal information incrementally in particular given a set of temporal constraints a temporal csp and a new constraint we want to maintain certain properties of the extended temporal csp e g a solution rather than recomputing them from scratch the point algebra pa and the interval algebra ia are two well known frameworks for qualitative temporal reasoning the reasoning algorithms for pa and the tractable fragments of ia such as nebel and burckert s maximal tractable class of relations ord horn have originally been designed for static reasoning in this paper we study the incremental version of the fundamental reasoning problems in the context of these tractable classes we propose a collection of new polynomial algorithms that can amortize their complexity when processing a sequence of input constraints to incrementally decide satisfiability to maintain a solution or to update the minimal representation of the csp our incremental algorithms improve the total time complexity of using existing static techniques by a factor of o n or o n2 where n is the number of the variables involved by the temporal csp an experimental analysis focused on constraints over pa confirms the computational advantage of our incremental approach

group decision making with a fuzzy linguistic majority abstract the determination of solutions in group decision making is considered the point of departure is a collection of individual fuzzy preference relations a solution is derived either directly from the individual fuzzy preference relations or by constructing first a social fuzzy preference relation as opposed to conventional approaches in which a crisp threshold type majority rule is used we employ a fuzzy majority rule specified by a fuzzy linguistic quantifier e g most much more than 50 etc a calculus of linguistically quantified propositions is applied using the fuzzy majority various solution concepts are derived mainly of the type of core minimax opposition set and consensus winner

on the concept of possibility probability consistency both probability and possibility may be seen as information about an experiment it is conceivable to have at some time these two forms of information about a same experiment and then the question of the relation between them arises at once in this paper some aspects of the concept of possibility probability consistency are studied the consistency is considered as a fuzzy property relative to the coherence between possibilistic and probabilistic information we analyse several measures of the degree of consistency and introduce an axiomatic to characterize them

programming in metric temporal logic abstract we present a fragment of metric temporal logic called bounded universal horn formulae as a theoretical basis for temporal reasoning in logic programming we characterize its semantics in terms of fixed points and canonical models and present an efficient proof method as operational semantics based on sld resolution with constraints although the complexity of real time logics is very high in general the validity problem for most of them is 1 l complete already for propositional fragments in case of dense time structures we show that the class of bounded universal horn formulae admits complete and efficient proof methods exploiting uniform proofs and linear time complexity of basic steps of the proof method the results obtained heavily rely on the fragment investigated and make it necessary to establish some basic results like compactness and approximation of the least model by at most steps of the corresponding fixed point operator directly without recourse to standard methods in dense case the fragment itself is sufficiently expressive for a variety of applications ranging from real time systems temporal deductive data bases and sequence evaluation purposes we show that the fragment is the greatest of the metric temporal logic in discrete and dense case having the properties classically desired for logic programming languages

inference with a single fuzzy conditional proposition abstract a topic in the area of approximate reasoning that has been extensively researched is the following given a single fuzzy conditional proposition if x then y is b with a and b being fuzzy sets defining particular values of the linguistic variables x and y respectively and given some a a then what can be inferred about the value of y when a us replaced by a in the works of l zadeh j baldwin e hisdal r yager m mizumoto et al different solutions to this problem were proposed though different they all share one common feature they ignore the fact that a single fuzzy conditional proposition represents only one specific manifestation of the causal influence exerted by x on y which is being described by binding the fuzzy set b to the fuzzy set a thus the general pattern of the causal relatinship between the two linguistic variables if forgotten as a result the inference made when the original value of x is replaced by a new one might in some cases contradict the general pattern of the causal relationship the present paper makes an attempt to specify these types of inference with a single fuzzy conditional proposition which do not depend on the general pattern of the causal relationship between x and y it also discusses some associated problems

fuzzy system technologies at siemens r d abstract applications of fuzzy logic are usually identified with fuzzy control but besides fuzzy control there are many other fuzzy theories that are used in applications among them fuzzy classification and diagnosis fuzzy control has to do with closed loops but besides the large amount of fuzzy control applications there are many other fuzzy theories being used in applications among them fuzzy classification and diagnosis we consider several recent results in fuzzy control and show their use in applications furthermore we give some examples of applications in fuzzy classification and fuzzy diagnosis

automated fuzzy and probabilistic inference abstract this paper illustrates the use of fril in the solution of inference problems under uncertainty and certain recursive functional equations various aspects of fril discussed include depth and breadth strategies backtracking mechanism and relational algebraic operation examples of the application of the theory to expert systems and decision support systems are provided

commonsense reasoning about causality deriving behavior from structure abstract this paper presents a qualitative reasoning method for predicting the behavior of mechanisms characterized by continuous time varying parameters the structure of a mechanism is described in terms of a set of parameters and the constraints that hold among them essentially a qualitative differential equation the qualitative behavior description consists of a discrete set of time points at which the values of the parameters are described in terms of ordinal relations and directions of change the behavioral description or envisionment is derived by two sets of rules propagation rules which elaborate the description of the current time point and prediction rules which determine what is known about the next qualitatively distinct state of the mechanism a detailed example shows how the envisionment method can detect a previously unsuspected landmark point at which the system is in stable equilibrium

a critical examination of allen s theory of action and time abstract j f allen s theory of time and action is examined and found to be unsuitable for representing facts about continuous change a series of revisions to allen s theory is proposed in order to accommodate this possibility the principal revision is a diversification of the temporal ontology to include instants on the same footing as intervals a distinction is also made between two kinds of property called states of position and states of motion with respect to the logic of their temporal incidence as a consequence of these revisions it is also found necessary to diversify the range of predicates specifying temporal location finally it is argued that allen s category of processes is superfluous since it can be assimilated with the category of properties the implications of this assimilation for the representation of sentences containing verbs in the progressive aspect are discussed

algebraic approximation of dirichlet to neumann maps for the equations of linear elasticity abstract the absorbing boundary conditions defined on the interface between the sub domains are of major importance for the convergence of domain decomposition methods in linear elasticity optimal absorbing boundary conditions can be derived and are associated with a dirichlet to neumann map in this paper several original algebraic techniques of approximation of this dirichlet to neumann map are investigated asymptotic spectral and numerical analysis of these techniques are successively presented for linear elasticity problems various numerical experiments illustrate the convergence properties of these original techniques

reasoning about action i a possible worlds approach abstract reasoning about change is an important aspect of commonsense reasoning and planning in this paper we describe an approach to reasoning about change for rich domains where it is not possible to anticipate all situations that might occur the approach provides a solution to the frame problem and to the related problem that it is not always reasonable to explicitly specify all of the consequences of actions the approach involves keeping a single model of the world that is updated when actions are performed the update procedure involves constructing the nearest world to the current one in which the consequences of the actions under consideration hold the way we find the nearest world is to construct proofs of the negation of the explicit consequences of the expected action and to remove a premise in each proof from the current world computationally this construction procedure appears to be tractable for worlds like our own where few things tend to change with each action or where change is regular

constructing membership functions using statistical data abstract determination of the membership functions is vital in practical applications of the fuzzy set theory this paper presents a guideline to construct the membership functions for fuzzy sets whose elements have a defining feature with a known probability density function pdf in the universe of discourse the method finds the smallest fuzzy set which assigns high average membership values to those objects with the defining features distributed according to the given pdf it is show that for any pdf the method is capable of generating membership functions in accordance with the possibility probability consistency principle membership functions derived from some of the well known pdfs and an application in solving noise contaminated linear system of equations are presented

order sorted logic programming with predicate hierarchy order sorted logic has been formalized as first order logic with sorted terms where sorts are ordered to build a hierarchy called a sort hierarchy these sorted logics lead to useful expressions and inference methods for structural knowledge that ordinary first order logic lacks nitta et al pointed out that for legal reasoning a sort hierarchy or a sorted term is not sufficient to describe structural knowledge for event assertions which express facts caused at some particular time and place the event assertions are represented by predicates with n arguments i e n ary predicates and then a particular kind of hierarchy called a predicate hierarchy is built by a relationship among the predicates to deal with such a predicate hierarchy which is more intricate than a sort hierarchy nitta et al implemented a typed sorted logic programming language extended to include a hierarchy of verbal concepts corresponding to predicates however the inference system lacks a theoretical foundation because its hierarchical expressions exceed the formalization of order sorted logic in this paper we formalize a logic programming language with not only a sort hierarchy but also a predicate hierarchy this language can derive general and concrete expressions in the two kinds of hierarchies for the hierarchical reasoning of predicates we propose a manipulation of arguments in which surplus and missing arguments in derived predicates are eliminated and supplemented as discussed by allen mcdermott and shoham in research on temporal logic and as applied by nitta et al to legal reasoning if each predicate is interpreted as an event or action not as a static property then missing arguments should be supplemented by existential terms in the argument manipulation based on this we develop a horn clause resolution system extended to add inference rules of predicate hierarchies with a semantic model restricted by interpreting a predicate hierarchy the soundness and completeness of the horn clause resolution is proven

optimal schwarz waveform relaxation for the one dimensional wave equation we introduce a nonoverlapping variant of the schwarz waveform relaxation algorithm for wave propagation problems with variable coefficients in one spatial dimension we derive transmission conditions which lead to convergence of the algorithm in a number of iterations equal to the number of subdomains independently of the length of the time interval these optimal transmission conditions are in general nonlocal but we show that the nonlocality depends on the time interval under consideration and we introduce time windows to obtain optimal performance of the algorithm with local transmission conditions in the case of piecewise constant wave speed we show that convergence in two iterations can be achieved independently of the number of subdomains in that case the algorithm thus scales optimally with the number of subdomains provided the time windows are chosen appropriately for continuously varying coefficients we prove convergence of the algorithm with local transmission conditions using energy estimates we then introduce a finite volume discretization which permits computations on nonmatching grids and we prove convergence of the fully discrete schwarz waveform relaxation algorithm we finally illustrate our analysis with numerical experiments

some properties of choice functions based on valued binary relations abstract choice functions based on t norms of valued binary relations are introduced strict preference is also specified with the use of a t norm properties of the choice functions are investigated and rationality conditions are studied some classical particular cases are presented

after the fuzzy wave reached europe abstract we briefly describe the situation of the fuzzy community in europe before the fuzzy wave we show that there was a lot of expertise in almost all subareas of fuzzy logic then we describe some aspects of the fuzzy wave itself in particular fuzzy control and first generation fuzzy systems that played a role during the time the fuzzy wave reached europe we also make some remarks about european companies and their activities during this time then we discuss the situation after the fuzzy wave some aspects of second generation fuzzy systems the combination of fuzzy logic with other theories and techniques and some new application areas finally we will discuss the chances of fuzzy systems in europe in the future

comparison of the probabilistic approximate classification and the fuzzy set model abstract it is shown that the generalized notion probabilistic approximate classification of rough sets can be conveniently described by the concept of fuzzy sets a discussion of the proper choice of the definition for the membership function of the intersection union of fuzzy sets is also presented however from the point of view of the probabilistic approximation space it is argued that there does not exist a universal definition for the fuzzy intersection union operation

motivated action theory a formal theory of causal reasoning when we reason about change over time it causation provides an implicit preference we prefer sequences of situations in which one situation leads causally to the next rather than sequences in which one situation follows another at random and without causal connections in this paper we explore the problem of temporal reasoning reasoning about change over time and the crucial role that causation plays in our intuitions we examine previous approaches to temporal reasoning and their shortcomings in light of this analysis we propose a new system for it causal reasoning motivated action theory which builds upon causation as a crucial preference criterion motivated action theory solves the traditional problems of both forward and backward reasoning and additionally provides a basis for a new theory of explanation

approximate reasoning with time abstract the need to make time dependent assumptions is frequently encountered in many systems especially in dynamical systems this paper presents a theoretical study of the representation and manipulation of some vague concepts in the temporally changing world our approach to the modeling is based on zadeh s theory of possibility we introduce a concept of similarity index in reasoning with time we present two different types of widely used models one rule based and another resolution based for reasoning with time we consider simply yet concrete examples to illustrate the usefulness of the proposed models

absorbing boundary conditions for time harmonic wave propagation in discretized domains while many successful absorbing boundary conditions abcs are developed to simulate wave propagation into unbounded domains most of them ignore the effect of interior discretization and result in spurious reflections at the artificial boundary we tackle this problem by developing abcs directly for the discretized wave equation specifically we show that the discrete system mesh can be stretched in a non trivial way to preserve the discrete impedance at the interface similar to the perfectly matched layers pml for continuous wave equation the stretch is designed to introduce dissipation in the exterior resulting in a pml type abc for discrete media the paper includes detailed formulation of the new discrete abc along with the illustration of its effectiveness over continuous abcs with the help of error analysis and numerical experiments for time harmonic problems the improvement over continuous abcs is achieved without any computational overhead leading to the conclusion that the discrete abcs should be used in lieu of continuous abcs

preference relations on a set of fuzzy utilities as a basis for decision making abstract in fuzzy decision problems we often encounter situations of choosing among alternatives which are assigned fuzzy utilities these problems have been approached using fuzzy implications or direct comparisons among fuzzy utilities in the literature however there are few attempts to investigate the issues addressing reasonable choice or reasonable ordering using fuzzy sets theory this paper first introduces some fundamental properties of fuzzy binary relations and certain conditions of reasonable orderings of fuzzy utilities then a method for constructing a fuzzy preference relation on a given set of fuzzy utilities is proposed for the sake of rational decision making this procedure employs the concepts of the extended minimum and the hamming distance between the greatest upper sets or the greatest lower sets of fuzzy utilities finally it is shown that the proposed fuzzy preference relations have reasonable properties as fuzzy orderings for decision making

a logic of time chance and action for representing plans abstract this paper integrates logical and probabilistic approaches to the representation of planning problems by developing a first order logic of time chance and action we start by making explicit and precise commonsense notions about time chance and action central to the planning problem we then develop a logic the semantics of which incorporates these intuitive properties the logical language integrates both modal and probabilistic constructs and allows quantification over time points probability values and domain individuals probability is treated as a sentential operator in the language so it can be arbitrarily nested and combined with other logical operators the language can represent the chance that facts hold and events occur at various times it can represent the chance that actions and other events affect the future the model of action distinguishes between action feasibility executability and effects we present a proof theory for the logic and show how the logic can be used to describe actions in such a way that the action descriptions can be composed to infer properties of plans via the proof theory

stablization of an inverted pendulum by a high speed fuzzy logic controller hardware system abstract a high speed fuzzy controller hardware system employing min max operations is presented it has fifteen control rule boards and one defuzzifier grades of membership are represented with 0 v 5 v corresponding to 0 0 1 0 this fuzzy controller facilitates approximate reasoning at 1 000 000 fips fuzzy inferences per second and is able to be used for various purposes by programming on each control rule board it handles fuzzy linguistic information of the form nl negative large nm negative medium ns negative small zr approximately zero ps positive small pm positive medium pl positive large and ng negation this fuzzy controller hardware system makes an inverted pendulum stand on a vehicle by using seven control rules two pendulums 5 mm diameter 15 cm length 3 5 g weight respectively 10 mm 50 cm and 50 g can be stabilized by the same rule set it is much easier to produce control rules than to solve the nonlinear differential equations representing the dynamics of an inverted pendulum this fuzzy controller hardware system can be applied to attitude control of a space booster rocket and satellite an automatic aircraft landing system pattern recognition stabilization of nuclear fuel rods in a reactor an intelligent sensor and many other applications which need swift approximate reasoning

absorbing boundary conditions for the wave equation and parallel computing absorbing boundary conditions have been developed for truncating unbounded computational domains to bounded ones the authors investigate the use of absorbing boundary conditions in domain decomposition algorithms for the wave equation moreover they optimize the absorbing boundary conditions in order to obtain a good performance of the schwarz waveform relaxation algorithm the analysis given is confirmed by numerical experiments

theory and methodologysome properties of choice functions based on valued binary relations choice functions based on t norms of valued binary relations are introduced strict preference is also specified with the use of a t norm properties of the choice functions are investigated and rationality conditions are studied some classical particular cases are presented

a non reified temporal logic abstract a temporal logic is presented for reasoning about propositions whose truth values might change as a function of time the temporal propositions consist of formulae in a sorted first order logic with each atomic predicate taking some set of temporal arguments as well as a set of non temporal arguments the temporal arguments serve to specify the predicate s dependence on time by partitioning the terms of the language into two sorts temporal and non temporal time is given a special syntactic and semantic status without having to resort to reification the benefits of this logic are that it has a clear semantics and a well studied proof theory unlike the first order logic presented by shoham propositions can be expressed and interpreted with respect to any number of temporal arguments not just with respect to a pair of time points an interval we demonstrate the advantages of this flexibility in addition nothing is lost by this added flexibility and more standard and usable syntax to prove this assertion we show that the logic completely subsumes shoham s temporal logic 19

a unifying semantics for time and events we give a formal semantics for a highly expressive language for representing temporal relationships and events this language which we call versatile event logic vel provides a general temporal ontology and semantics encompassing many other representations the system incorporates a number of features that have not been widely employed in ai formalisms it has the ability to describe alternative histories using a modal operator it provides a semantics for individuals that explicitly models their identity through time and across alternative possible histories and enables one to distinguish between necessary and extensional identity of individuals in virtue of its treatment of individuals and count nouns the formalism offers a solution to certain puzzles of identity which arise when individuals are described in different ways we propose that vel can be used as a foundational interlingua for comparing and interfacing different ai languages and illustrate this by considering how situation calculus and event calculus can be represented within vel

absorbing boundary conditions for the discretization schemes of the one dimensional wave equation when computing a partial differential equation it is often necessary to introduce artificial boundaries here we explain a systematic method to obtain boundary conditions for the wave equation in one dimension fitting to the discretization scheme and stable moreover we give error estimates on the reflected part

high order numerical sommerfeld boundary conditions theory and experiments abstract we develop high order non reflecting boundary equations for a semidiscrete approximation of the simple hyperbolic advection equation u 1 cu x 0 these boundary equation are based on a discrete interpretation of sommerfeld s radiation condition for a second order wave equation which is associated with the semi discrete equation the performance of these schemes is expressed by an exact measure of the energy reflected at the boundary for low order cases the discrete sommerfeld boundary equations are identical with the standard finite difference equations but for high orders of approximation starting with 4 points the discrete sommerfeld schemes differ from standard finite differences it is shown and verified experimentally that the discrete sommerfeld schemes are optimal in the sense that they produce the least amount of reflected energy moreover it is known theoretically and we verify experimentally that the reflected energy remains invariat when the semi discrete equation are time discretized with the trapezoidal crank nicolson method the corresponding fully discrete boundary equations are thus also optimal in the sense that they minimize the reflected energy

an adaptive control method for time varying systems abstract fuzzy set theory has grown to become a major scientific domain collectively referred to as fuzzy systems it has been shown that there are a lot of applications in almost all sub areas of fuzzy systems however the most successful application has been in fuzzy control fuzzy control algorithms have been extensively used in business and industry in this paper an adaptive control technique based on the fuzzy parameter identification is presented the application of this technique includes an example in agriculture

algebraic structures in fuzzy logic abstract common features in various fuzzy logical systems are investigated it turns out that adjoint couples and residuated lattices are very often present though not always explicitly expressed some minor new results are also proved

representation and use of imprecise temporal knowledge in dynamic systems abstract in this paper the importance of representation and use of imprecise temporal knowledge for problem solving in industrial dynamic systems is emphasized first a representation of imprecise temporal knowledge is then given for describing the dynamic behavior of systems a novel problem on on line temporal matching and numeric matching is presented and a method for solving this problem is proposed a method for fuzzy proposition reasoning and temporal reasoning is put forward finally as two application examples the fault diagnosis of a fluidized catalytic cracking unit is taken up to illustrate the usefulness of the proposed knowledge representation and methods

absorbing interface conditions for domain decomposition methods a general presentation the continuity conditions and the transmission conditions involved in domain decomposition methods are of major importance for the fast and robust convergence of these algorithms in this review paper we study step by step the methodology to derive various continuity conditions and compatible transmission conditions for two different types of problems i e the laplace equation and the helmholtz equation an original homogeneous formulation is also presented both in the continuous and in the discrete analysis numerical experiments show the relative efficiency of these continuity conditions and of these transmission conditions on academic problems

reasoning about qualitative temporal information abstract representing and reasoning about incomplete and indefinite qualitative temporal information is an essential part of many artificial intelligence tasks an interval based framework and a point based framework have been proposed for representing such temporal information in this paper we address two fundamental reasoning tasks that arise in applications of these frameworks given possibly indefinite and incomplete knowledge of the relationships between some intervals or points i find a scenario that is consistent with the information provided and ii find the feasible relations between all pairs of intervals or points for the point based framework and a restricted version of the interval based framework we give computationally efficient procedures for finding a consistent scenario and for finding the feasible relations our algorithms are marked improvements over the previously known algorithms in particular we develop an o n2 time algorithm for finding one consistent scenario that is an o n improvement over the previously known algorithm where n is the number of intervals or points and we develop an algorithm for finding all the feasible relations that is of far more practical use than the previously known algorithm for the unrestricted version of the interval based framework finding a consistent scenario and finding the feasible relations have been shown to be np complete we show how the results for the point algebra aid in the design of a backtracking algorithm for finding one consistent scenario that is shown to be useful in practice for planning problems

temporal constraint satisfaction on causal models abstract causal models play a fundamental role in many intelligent problem solving activities such as diagnosis or simulation although the notion of causation is strictly related to the notion of time temporal knowledge and temporal reasoning have been often disregarded in problem solvers operating on causal models in this page we propose an approach to temporal constraint satisfaction on causal models the approach departs significantly from traditional approaches to temporal constraint satisfaction in our approach in fact we use synchronization mechanisms for dealing with events caused by a conjunction of other events in the paper we analyze the computation complexity of temporal constraint satisfaction on causal models showing that such a form of reasoning is intrinsically intractable i e it is intractable even if one limits the attention to a simple form of causal model and of consistency constraints however we show that it is possible to define sufficient conditions for temporal consistency that can be checked in polynomial time interestingly such conditions allow us to relate our approach to traditional approaches to temporal constraint satisfaction

towards a general theory of action and time abstract a formalism for reasoning about actions is proposed that is based on a temporal logic it allows a much wider range of actions to be described than with previous approaches such as the situation calculus this formalism is then used to characterize the different types of events processes actions and properties that can be described in simple english sentences in addressing this problem we consider actions that involve non activity as well as actions that can only be defined in terms of the beliefs and intentions of the actors finally a framework for planning in a dynamic world with external events and multiple agents is suggested

solvability of fuzzy relational equations and manipulation of fuzzy data abstract the problem of characterization of fuzzy relational equations with respect to their solvability property is studied some aspects of manipulation of fuzzy data with the aid of fuzzy relational equations are considered two stages of manipulation process are indicated combining pieces of evidence and inferring their mutual correspondence both of them are formulated and solved by the use of fuzzy relational equations the role of a solvability index is extensively studied numerical considerations give an illustration of the approach we propose and deal with some real data used for fuzzy controllers

the measure of the degree of truth and the grade of membership abstract a method is presented to define the meaning of a fuzzy proposition and of a fuzzy set through the construction of fuzzy propositions with non ambiguous intermediate truth values

backtracking algorithms for disjunctions of temporal constraints abstract we extend the framework of simple temporal problems studied originally by dechter meiri and pearl to consider constraints of the form x 1 y 1 r 1 x n y n r n where x 1 x n y 1 y n are variables ranging over the real numbers r 1 r n are real constants and n 1 this is a wide class of temporal constraints that can be used to model a variety of problems in temporal reasoning scheduling planning and temporal constraint databases we have implemented several progressively more efficient algorithms for the consistency checking problem for this class of temporal constraints backtracking backjumping three variations of forward checking and forward checking with backjumping we have partially ordered the above algorithms according to the number of visited search nodes and the number of performed consistency checks although our problem is non binary our results agree with the results of kondrak and van beek who consider only binary constraints we have also studied the performance of the above algorithms experimentally using randomly generated sets of data and job shop scheduling problems the experiments with random instances allowed us to locate the hard region for this class of problems the results show that hard problems occur at a critical value of the ratio of disjunctions to variables

the token reification approach to temporal reasoning abstract the approach to temporal reasoning which has proven most popular in ai is the reified approach in this approach one introduces names for events and states and uses special predicates to assert that an event or state occurs or holds at a particular time however recently the reified approach has come under attack both on technical and on ontological grounds thus it has been claimed that at least some reified temporal logics do not give one more expressive power than provided by alternative approaches moreover it has been argued that the reification of event and state types in reified temporal logics rather than event and state tokens makes the ontology more complicated than necessary in this paper we present a new reified temporal logic called trl which we believe avoids most of these objections it is based on the idea of reifying event tokens instead of event types however unlike other such attempts our logic contains meaningful names for event tokens thus allowing us to quantify over all event tokens that meet a certain criterion the resulting logic is more expressive than alternative approaches moreover it avoids the ontologically objectionable reification of event types while staying within classical first order predicate logic

an accuracy analysis of boundary conditions for the forced shallow water equations the accuracy of numerical boundary conditions for the linearized one dimensional shallow water equations is determined by extending the dispersion fourier analysis originally presented by c k chu and a sereny j comput phys 15 476 1974 accuracy is measured by calculating steady state amplitudes of incoming and outgoing numerical waves at a boundary as functions of a forcing frequency radiating closed and forced radiating boundary conditions are studied in combination with two numerical schemes the richardson sielecki explicit finite difference scheme and the galerkin finite element method with piecewise linear basis functions and crank nicolson time stepping contamination of the finite element solution with short waves is seen to vary with the choice of extraneous boundary conditions an example of l n trefethen s j comput phys 49 199 1983 interpretation of the b gustafsson h kreiss and a sundstrom math comput 26 649 1972 instability is also given for the finite element method

constraint propagation with interval labels abstract constraint propagation is often used in ai systems to perform inference about quantities this paper studies one particular kind of constraint propagation where quantities are labelled with signs or with intervals and these labels are propagated through recorded constraints we review the uses of such inference schemes in ai systems of various kinds and evaluate their strengths and weaknesses in particular we determine the completeness and running time of constraint propagation for various kinds of labels and constraints

representing preferences using intervals in this paper we present a general framework for the comparison of intervals when preference relations have to established the use of intervals in order to take into account imprecision and vagueness in handling preferences is well known in the literature but a general theory on how such models behave is lacking in the paper we generalize the concept of interval allowing the presence of more than two points we then introduce the structure of the framework based on the concept of relative position and component set we provide an exhaustive study of 2 point and 3 point intervals comparison and show the way to generalize such results to n point intervals

the topology of boundaries abstract high level representations used in reasoning distinguish a special set of boundary locations at which function values can change abruptly and across which adjacent regions may not be connected standard models of space and time based on segmenting r n do not allow these possibilities because they have the wrong topological structure at boundaries this mismatch has made it difficult to develop formal mathematical models for high level reasoning algorithms this paper shows how to modify an r n model so as to have an appropriate topological structure it then illustrates how the new models support standard reasoning algorithms provide simple models for previously difficult situations and suggest interesting new analyses based on change or non change in scene topology

reasoning about temporal relations a maximal tractable subclass of allen s interval algebra we introduce a new subclass of allen s interval algebra we call ord horn subclass which is a strict superset of the pointisable subclass we prove that reasoning in the ord horn subclass is a polynomial time problem and show that the path consistency method is sufficient for deciding satisfiability further using an extensive machine generated case analysis we show that the ord horn subclass is a maximal tractable subclass of the full algebra assuming p np in fact it is the unique greatest tractable subclass amongst the subclasses that contain all basic relations

foundations of fuzzy sets abstract this paper gives an overview of the origins of fuzzy set theory and the problems for the foundations of fuzzy sets arising from those origins and current practice it then gives detailed accounts of categorical approaches using a closed structure to capture the fuzzy and connective within these categories weak forms of subobject representations provide an internal second order logic an approach to fuzzy real numbers and fuzzy topology is included to illustrate the use of this internal second order theory

fuzzy constraint networks for signal pattern recognition this paper deals with representation and reasoning on information concerning the evolution of a physical parameter by means of a model based on the fuzzy constraint satisfaction problem formalism and with which it is possible to define what we call fuzzy temporal profiles ftp based on fundamentally linguistic information this model allows the integration of knowledge on the evolution of a set of parameters into a knowledge representation scheme in which time plays a fundamental role the ftp model describes the behaviour of a physical parameter on the basis of a set of signal events and which allows the evolution of the parameter between each pair of events to be modelled as signal episodes given the fundamentally linguistic nature of the information represented the consistency analysis of this information is an essential task nevertheless the obtention of the minimal representation of the network that defines an ftp is an np hard problem in spite of this we supply algorithms guaranteeing local levels of consistency that allow to correct a large proportion of the errors committed by a human expert in the linguistic description of the profile furthermore we propose a new topology whose consistency can be guaranteed in polynomial time we also study the applicability of this model in the recognition of signal patterns