The token reification approach to temporal reasoning (original) (raw)
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A series of temporal reasoning tasks are identified which motivate the consideration and application of temporal logics in artificial intelligence. There follows a discussion of the broad issues involved in modelling time and constructing a temporal logic. The paper then presents a detailed review of the major approaches to temporal logics: first-order logic approaches, modal temporal logics and reified temporal logics. The review considers the most significant exemplars within the various approaches, including logics due to Russell, Hayes and McCarthy, Prior, McDermott, Allen, Kowalski and Sergot. The logics are compared and contrasted, particularly in their treatments of change and action, the roles they seek to fulfil and the underlying models of time on which they rest. The paper concludes with a brief consideration of the problem of granularity-a problem of considerable significance in temporal reasoning, which has yet to be satisfactorily treated in a temporal logic.
A temporal logic for reasoning about processes and plans*
Cognitive science, 1982
Much previous work in artificial intelligence has neglected representing time in all its complexity. In particular, it has neglected continuous change and the indeterminacy of the future. To rectify this, I have developed a first-order temporal logic, in which it is possible to name and prove things about facts, events, plans, and world histories. In particular, the logic provides analyses of causality, continuous change in quantities, the persistence of facts (the frame problem), and the relationship between tasks and actions. It may be possible to implement a temporal-inference machine based on this logic, which keeps track of several "maps" of a time line, one per possible history.
A Formalism for Representing and Reasoning with Temporal Information, Event and Change
Applied Intelligence, Vol. 23, No. 2. 109-119, 2005
In this paper we present a general formalism for representing and reasoning with temporal information, event and change. The temporal framework is a theory of time that takes both points and interval as temporal primitives and where the base logic is that of Kleene's three-valued logic. Thus, we can avoid the Divided Instant Problem (DIP). We present a three-valued based Temporal First-Order Nonmonotonic Logic (TFONL) that employs an explicit representation of time and events. We may embody default logic into TFONL, which takes into consideration the frame, qualification and ramification problems.
Reified Temporal Theories and How to Unreify Them
1991
Reification of propositions expressing states, events, and properties has been widely advocated as a means of handling temporal reasoning in AI. The author proposes that such reification is both philosophically suspect and technically unnecessary. The reified theories of Allen and Shoham are examined and it is shown how they can be unreified. The resulting loss of expressive power can be rectified by adopting Davidson's theory in which event tokens, rather than event types, are reified. This procedure is illustrated by means of Kowalski and Sergot's Event Calculus, the additional type-reification of the latter system being excised by means of a general procedure proposed by the author for converting type-reification into token-reification. Some examples are given to demonstrate the expressive power of the resulting theory.
Temporal logic and reasoning about actions
1996
Abstract This paper shows how past temporal logic can be incorporated into the action description language A 4] and its extensions. Incorporating past temporal logic will allow us to elegantly express e ects of actions that depend not only on the current state of the world but on previous actions and states. It will also allow us to elegantly express dynamic constraints beyond the one-step dynamic constraints discussed in 2].
A unifying semantics for time and events
Artificial Intelligence, 2004
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.
A Temporal Description Logic for Reasoning about Actions and Plans
Journal of Artificial Intelligence Research, 1998
A class of interval-based temporal languages for uniformly representing and reasoning about actions and plans is presented. Actions are represented by describing what is true while the action itself is occurring, and plans are constructed by temporally relating actions and world states. The temporal languages are members of the family of Description Logics, which are characterized by high expressivity combined with good computational properties. The subsumption problem for a class of temporal Description Logics is investigated and sound and complete decision procedures are given. The basic language TL-F is considered rst: it is the composition of a temporal logic TL { able to express interval temporal networks { together with the non-temporal logic F { a Feature Description Logic. It is proven that subsumption in this language is an NP-complete problem. Then it is shown how to reason with the more expressive languages TLU-FU and TL-ALCF. The former adds disjunction both at the temporal and non-temporal sides of the language, the latter extends the non-temporal side with set-valued features (i.e., roles) and a propositionally complete language.
Temporal reasoning with classes and instances of events
Proceedings Ninth International Symposium on Temporal Representation and Reasoning
Representing and reasoning with both temporal constraints between classes of events (e.g., between the types of actions needed to achieve a goal) and temporal constraints between instances of events (e.g., between the specific actions being executed) is a ubiquitous task in many areas of computer science, such as planning, workflow, guidelines and protocol management. The temporal constraints between the classes of events must be inherited by the instances, and the consistency of both types of constraints must be checked. In this paper, we propose a general-purpose domain-independent knowledge server dealing with these issues. In particular, we propose a formalism to represent temporal constraints, we show two algorithms to deal with inheritance and to perform temporal consistency checking, and we study the properties of the algorithms.
TEMPORAL ENTITIES - Types, Tokens and Qualifications
International Conference on Knowledge Engineering and Ontology Development, 2018
Reified logics have been a major subject of interest in the knowledge representation community for well over twenty years, since over the years, the need to quantify and reason about propositional entities such as events and states among other temporal entities has grown. Galton had made it clear that one may either refer to types or tokens (instances) of such entities in the ontology. A clear tendency in the literature is to derive event tokens from event types by instantiating types with their times of occurrence. That tendency is exemplified by earlier token-reified logic. The problem with this approach is that it makes it difficult to distinguish between two different events of the same type happening at the same time. This is a major price that earlier logic paid for being a full-fledged logical theory. This paper presents an alternative way of deriving event tokens from event types which uses the concept of qualifications rather than use times of occurrence. A clear distinction is made between qualifications and the actual event tokens they help derive from event types. A qualification captures the peculiarities of an actual event token that are not part of the event type definitions. Our logic maintains both the advantage of being a full-fledged logic as well being able to add many qualifications to an event token.
Temporal representation and reasoning in artificial intelligence: A review
Mathematical and Computer Modelling, 2001
The exphclt representation and ressonmg about time 1s an Important problem m many areas of artHiclal mtelhgence Over the last l&15 years, It has been attractmg the attention of many researchers Several temporal reasonmg systems, dlffermg m design issues related to ontology of time, underlying temporal logic, temporal constramts used and algorithms employed, have been developed In this survey, Important representatIona issues which determme a temporal reasonmg system are introduced