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16
A Scheme for Integrating Concrete Domains into Concept Languages
, 1991
"... A drawback which concept languages based on klone have is that all the terminological knowledge has to be defined on an abstract logical level. In many applications, one would like to be able to refer to concrete domains and predicates on these domains when defining concepts. Examples for such conc ..."
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Cited by 262 (20 self)
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A drawback which concept languages based on klone have is that all the terminological knowledge has to be defined on an abstract logical level. In many applications, one would like to be able to refer to concrete domains and predicates on these domains when defining concepts. Examples for such concrete domains are the integers, the real numbers, or also nonarithmetic domains, and predicates could be equality, inequality, or more complex predicates. In the present paper we shall propose a scheme for integrating such concrete domains into concept languages rather than describing a particular extension by some specific concrete domain. We shall define a terminological and an assertional language, and consider the important inference problems such as subsumption, instantiation, and consistency. The formal semantics as well as the reasoning algorithms are given on the scheme level. In contrast to existing klone based systems, these algorithms will be not only sound but also complete. The...
Terminological Reasoning is Inherently Intractable
 ARTIFICIAL INTELLIGENCE
, 1990
"... Computational tractability has been a major concern in the area of terminological knowledge representation and reasoning. However, all analyses of the computational complexity of terminological reasoning are based on the hidden assumption that subsumption in terminologies reduces to subsumption of c ..."
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Cited by 147 (11 self)
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Computational tractability has been a major concern in the area of terminological knowledge representation and reasoning. However, all analyses of the computational complexity of terminological reasoning are based on the hidden assumption that subsumption in terminologies reduces to subsumption of concept descriptions without a significant increase in computational complexity. In this paper it will be shown that this assumption, which seems to work in the "normal case," is nevertheless wrong. Subsumption in terminologies turns out to be coNPcomplete for a minimal terminological representation language that is a subset of every useful terminological language.
Embedding Defaults into Terminological Knowledge Representation Formalisms
 Journal of Automated Reasoning
, 1995
"... We consider the problem of integrating Reiter's default logic into terminological representation systems. It turns out that such an integration is less straightforward than we expected, considering the fact that the terminological language is a decidable sublanguage of firstorder logic. Semanticall ..."
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Cited by 125 (6 self)
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We consider the problem of integrating Reiter's default logic into terminological representation systems. It turns out that such an integration is less straightforward than we expected, considering the fact that the terminological language is a decidable sublanguage of firstorder logic. Semantically, one has the unpleasant effect that the consequences of a terminological default theory may be rather unintuitive, and may even vary with the syntactic structure of equivalent concept expressions. This is due to the unsatisfactory treatment of open defaults via Skolemization in Reiter's semantics. On the algorithmic side, we show that this treatment may lead to an undecidable default consequence relation, even though our base language is decidable, and we have only finitely many (open) defaults. Because of these problems, we then consider a restricted semantics for open defaults in our terminological default theories: default rules are only applied to individuals that are explicitly presen...
How to Prefer More Specific Defaults in Terminological Default Logic
 In Proceedings of the International Joint Conference on Artificial Intelligence
, 1993
"... In a recent paper we have proposed terminological default logic as a formalism which combines both means for structured representation of classes and objects, and for default inheritance of properties. The major drawback which terminological default logic inherits from general default logic is t ..."
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Cited by 49 (1 self)
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In a recent paper we have proposed terminological default logic as a formalism which combines both means for structured representation of classes and objects, and for default inheritance of properties. The major drawback which terminological default logic inherits from general default logic is that it does not take precedence of more specific defaults over more general ones into account. This behaviour has already been criticized in the general context of default logic, but it is all the more problematic in the terminological case where the emphasis lies on the hierarchical organization of concepts. The present paper addresses the problem of modifying terminological default logic such that more specific defaults are preferred. It turns out that the existing approaches for expressing priorities between defaults do not seem to be appropriate for this purpose. Therefore we shall consider an alternative approach for dealing with prioritization in the framework of Reiter's def...
A MultiDimensional Terminological Knowledge Representation Language
, 1995
"... An extension of the concept description language ALC used in klonelike terminological reasoning is presented. The extension includes multimodal operators that can either stand for the usual role quantifications or for modalities such as belief, time etc. The modal operators can be used at all lev ..."
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Cited by 34 (2 self)
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An extension of the concept description language ALC used in klonelike terminological reasoning is presented. The extension includes multimodal operators that can either stand for the usual role quantifications or for modalities such as belief, time etc. The modal operators can be used at all levels of the concept terms, and they can be used to modify both concepts and roles. This is an instance of a new kind of combination of modal logics where the modal operators of one logic may operate directly on the operators of the other logic. Different versions of this logic are investigated and various results about decidability and undecidability are presented. The main problem, however, decidability of the basic version of the logic, remains open.
Modal description logics: Modalizing roles
 Fundam. Inform
, 1999
"... In this paper, we construct a new concept description language intended for representing dynamic and intensional knowledge. The most important feature distinguishing this language from its predecessors in the literature is that it allows applications of modal operators to all kinds of syntactic term ..."
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Cited by 31 (14 self)
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In this paper, we construct a new concept description language intended for representing dynamic and intensional knowledge. The most important feature distinguishing this language from its predecessors in the literature is that it allows applications of modal operators to all kinds of syntactic terms: concepts, roles and formulas. Moreover, the language may contain both local (i.e., statedependent) and global (i.e., stateindependent) concepts, roles and objects. All this provides us with the most complete and natural means for re ecting the dynamic and intensional behaviour of application domains. We construct a satis ability checking (mosaictype) algorithm for this language (based on ALC) in(i) arbitrary multimodal frames, (ii) frames with universal accessibility relations (for knowledge) and (iii) frames with transitive, symmetrical and euclidean relations (for beliefs). On the other hand, it is shown that the satisfaction problem becomes undecidable if the underlying frames are arbitrary strict linear orders, hN; <i, or the language contains the common knowledge operator for n 2 agents. 1
Terminological logics with modal operators
, 1994
"... Terminological knowledge representation formalisms can be used to represent objective, timeindependent facts about an application domain. Notions like belief, intentions, and time which are essential for the representation of multiagent environments can only be expressed in a very limited way. For ..."
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Cited by 27 (1 self)
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Terminological knowledge representation formalisms can be used to represent objective, timeindependent facts about an application domain. Notions like belief, intentions, and time which are essential for the representation of multiagent environments can only be expressed in a very limited way. For such notions, modal logics with possible worlds semantics provides a formally wellfounded and wellinvestigated basis. This paper presents a framework for integrating modal operators into terminological knowledge representation languages. These operators can be used both inside of concept expressions and in front of terminological and assertional axioms. We introduce syntax and semantics of the extended language, and show that satisfiability of finite sets of formulas is decidable, provided that all modal operators are interpreted in the basic logic K, and that the increasing domain assumption is used. 1
POPELHOW: A Distributed Parallel Model for Incremental Natural Language Production with Feedback
 In Proceedings of the Eleventh International Joint Conference on Artificial Intelligence
, 1989
"... This paper 1 presents a new model for the produc tion of natural language. The novel idea is to com bine incremental and bidirectional generation with parallelism. The operational basis of our model is a distributed parallel system at every level of repre sentation. Starting point of the production ..."
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Cited by 19 (8 self)
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This paper 1 presents a new model for the produc tion of natural language. The novel idea is to com bine incremental and bidirectional generation with parallelism. The operational basis of our model is a distributed parallel system at every level of repre sentation. Starting point of the production are seg ments of the conceptual level. These segments are related to active objects which have to map them selves across the linguistic levels (i.e. functionalsemantic, syntactic and morphologic level) as fast and as independently as possible. Therefore the in cremental behavior caused by a successive input is propagated on all levels. Linguistic requirements de tected by objects which are related to already pro duced segments at any level influence and restrict the decision of what to say next. 1
CLASP: Integrating Term Subsumption Systems and Production Systems
 IEEE Transactions on Knowledge and Data Engineering
, 1991
"... Rules and frames are two knowledge representation schemes whose strengths and weakness are complementary to each other. Although several previous systems have attempted to integrate the two, few efforts have been made to incorporate the terminological knowledge of the framebased systems into the ru ..."
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Cited by 16 (1 self)
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Rules and frames are two knowledge representation schemes whose strengths and weakness are complementary to each other. Although several previous systems have attempted to integrate the two, few efforts have been made to incorporate the terminological knowledge of the framebased systems into the rulebased paradigm. To achieve a deep integration of the two schemes, we have developed and implemented a CLASsificationbased Production system (CLASP). This paper describes two major processes of CLASP: a semantic pattern matcher and a pattern classifier. The semantic pattern matcher extends the pattern matching capabilities of rulebased systems through the use of terminological knowledge. The pattern classifier enables the system to compute a rule's specificity, which is useful for conflict resolution, based on the semantics of its left hand side. The paradigm not only enhances the reasoning capabilities of rulebased systems, but also helps to reduce the cost of maintaining such systems ...
Terminological Reasoning and Information Management
 INFORMATION SYSTEMS AND ARTIFICIAL INTELLIGENCE
, 1991
"... Reasoning with terminological logics is a subfield in the area of knowledge representation that evolved from the representation language klone. Its main purpose is to automatically determine the location of a a new concept description (or object description) in a partially ordered set of given con ..."
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Cited by 11 (0 self)
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Reasoning with terminological logics is a subfield in the area of knowledge representation that evolved from the representation language klone. Its main purpose is to automatically determine the location of a a new concept description (or object description) in a partially ordered set of given concepts. It seems to be a promising approach to apply the techniques developed in this area to the development of new objectbased database models. The main advantages are a uniform query and database definition language and the utilization of an indexing technique, which we call semantic indexing.