Translating description logics to information server queries

1994

ion is a weil known mechanism in reasoning about individuals in concept-based systems. It consists in retrieving all the assertions relevant to a given individual a and collecting them into a single concept. Such concept has the property of being the most specific concept (expressible in the language) such that the individual a is an instance of. For this reason it is generally indicated by MSC(a) (Most Specific Concept). Abstraction, together with subsumption, allows one to perform instance checking. In fact, an algorithm for checking whether A 1= C(a) can work as follows: Step 1. compute MSC(a). Step 2. check whether C subsurnes MSC(a). This algorithm, called Abstraction/Subsumption, has been broadly exploited in actual systems (see [Quantz and Kindermann,1990; Nebel,1990]) . However, the problem of exploiting this algorithm is that, in general, it is not possible to completely fit in the information relevant to an individual into a single concept of the language. Let us clarify t...

Foundations of Artificial Intelligence, 2008

In this chapter we will introduce description logics, a family of logic-based knowledge representation languages that can be used to represent the terminological knowledge of an application domain in a structured way. We will first review their provenance and history, and show how the field has developed. We will then introduce the basic description logic ALC in some detail, including definitions of syntax, semantics and basic reasoning services, and describe important extensions such as inverse roles, number restrictions, and concrete domains. Next, we will discuss the relationship between description logics and other formalisms, in particular first order and modal logics; the most commonly used reasoning techniques, in particular tableau, resolution and automata based techniques; and the computational complexity of basic reasoning problems. After reviewing some of the most prominent applications of description logics, in particular ontology language applications, we will conclude with an overview of other aspects of description logic research, and with pointers to the relevant literature.

Theory, Implementation and Applications, 2007

The purpose of the chapter is to help someone familiar with DLs to understand the issues involved in developing an ontology for some universe of discourse, which is to become a conceptual model or knowledge base represented and reasoned with using Description Logics. We briefly review the purposes and history of conceptual modeling, and then use the domain of a university library to illustrate an approach to conceptual modeling that combines general ideas of object-centered modeling with a look at special modeling/ontological problems, and DL-specific solutions to them. Among the ontological issues considered are the nature of individuals, concept specialization, non-binary relationships, materialization, aspects of part-whole relationships, and epistemic aspects of individual knowledge.

2002

Abstract Class-based languages express knowledge in terms of objects and classes, and have inspired a huge number of formalisms in computer science. Description logics forma family of both class-based and logic-based knowledge representation languages which allow for modeling an application domain in terms of objects, classes and relationships between classes, and for reasoning about them.

1999

inf.unibz.it, 1998

The article aims at establishing a logical approach to class-based data modeling. After a discussion on class-based formalisms for data modeling, we introduce a family of logics, called Description Logics, which stem from research on Knowledge Representation in Artificial Intelligence. The logics of this family are particularly well suited for specifying data classes and relationships among classes, and are equipped with both formal semantics and inference mechanisms. We demonstrate that several popular data modeling formalisms, including the Entity-Relationship Model, and the most common variants of object-oriented data models, can be expressed in terms of specific logics of the family. For this purpose we use a unifying Description Logic, which incorporates all the features needed for the logical reformulation of the data models used in the various contexts. We also discuss the problem of devising reasoning procedures for the unifying formalism, and show that they provide valuable supports for several important data modeling activities.

1999

The 1999 International Workshop on Description Logics was held in Link oping, Sweden from July 30 to August 1. It was an a liate event with the Sixteenth International Joint Conference on Arti cial Intelligence (IJCAI'99, Stockholm, July 31-August 6) and with the Sixth International Workshop on Knowledge Representation meets Databases (KRDB'99, Link oping, July 29-30).

2002

(L2 with “counting quantifiers”), known to be decidable✦ in contrast to most DLs, adding transitive roles (binary relations/transitive closure operator) to L2 leads to undecidability✦ many DLs (like many modal logics) are fragments of the Guarded Fragment✦ most DLs are less complex than L2:

The use of DL systems to add reasoning capabilities to database is now a major trend in convergence between knowledge base and database system but is still confronted with the issue of data update. DL systems provide fact additions and retractions but no real object update mechanisms. We present a semantics for update that favours attribute values to concept membership and deals with incomplete information. After relating our work to an existing previous one on update semantics we address implementation issues.

Handbook of Automated …, 2001