Сипаттамалық логикалар: Білімді формалдау тілдерінің отбасысы

Family of formal knowledge representation
Description logics (DL) are a family of formal knowledge representation languages. Many DLs are more expressive than propositional logic but less expressive than first order logic. In contrast to the latter, the core reasoning problems for DLs are (usually) decidable, and efficient decision procedures have been designed and implemented for these problems. There are general, spatial, temporal, spatiotemporal, and fuzzy description logics, and each description logic features a different balance between expressive power and reasoning complexity by supporting different sets of mathematical constructors. DLs are used in artificial intelligence to describe and reason about the relevant concepts of an application domain (known as terminological knowledge). It is of particular importance in providing a logical formalism for ontologies and the Semantic Web: the Web Ontology Language (OWL) and its profiles are based on DLs. The most notable application of DLs and OWL is in biomedical informatics where DL assists in the codification of biomedical knowledge.

A description logic (DL) models concepts, roles and individuals, and their relationships. The fundamental modeling concept of a DL is the axiom—a logical statement relating roles and/or concepts. This is a key difference from the frames paradigm where a frame specification declares and completely defines a class. allows:
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Concept intersection
Universal restrictions
Limited existential quantification
Role restriction
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Concept intersection
Existential restrictions (of full existential quantification)
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Followed by any of the following extensions:
Functional properties, a special case of uniqueness quantification. Full existential qualification (existential restrictions that have fillers other than ). Concept union. Complex concept negation. Role hierarchy (subproperties: rdfs:subPropertyOf). Limited complex role inclusion axioms; reflexivity and irreflexivity; role disjointness. Nominals. (Enumerated classes of object value restrictions: owl:oneOf, owl:hasValue). Inverse properties. Cardinality restrictions (owl:cardinality, owl:maxCardinality), a special case of counting quantification Qualified cardinality restrictions (available in OWL 2, cardinality restrictions that have fillers other than ). Use of datatype properties, data values or data types.

As an example, is a centrally important description logic from which comparisons with other varieties can be made. is simply with complement of any concept allowed, not just atomic concepts. is used instead of the equivalent
A further example, the description logic is the logic plus extended cardinality restrictions, and transitive and inverse roles. The naming conventions aren't purely systematic so that the logic might be referred to as and other abbreviations are also made where possible. The Protégé ontology editor supports Three major biomedical informatics terminology bases, SNOMED CT, GALEN, and GO, are expressible in (with additional role properties). OWL 2 provides the expressiveness of , OWL DL is based on , and for OWL Lite it is .

Description logic was given its current name in the 1980s. Previous to this it was called (chronologically): terminological systems, and concept languages.

Frames and semantic networks lack formal (logic based) semantics. DL was first introduced into knowledge representation (KR) systems to overcome this deficiency. RACER (2001), CEL (2005), and KAON 2 (2005). DL reasoners, such as FaCT, FaCT++, implement the method of analytic tableaux. KAON2 is implemented by algorithms which reduce a SHIQ(D) knowledge base to a disjunctive datalog program.

There are some semantic reasoners that deal with OWL and DL. These are some of the most popular:
CEL is an open source LISP based reasoner (Apache 2.0 License). Cerebra Engine was a commercial C++ based reasoner, acquired in 2006 by webMethods. FaCT++ is a free open source C++ based reasoner. KAON2 is a free (for non commercial use) Java based reasoner, offering fast reasoning support for OWL ontologies. MSPASS is a free open source C reasoner for numerous DL models. Pellet is a dual licensed (AGPL and proprietary) commercial, Java based reasoner. RacerPro of Racer Systems was a commercial (free trials and research licenses are available) lisp based reasoner, today both an open source version of RACER exists from the original developers at Lübeck University using the BSD 3 license, and also a commercialized version, still named RacerPro by Franz Inc.
Sim DL is a free open source Java based reasoner for the language ALCHQ. It also provides a similarity measurement functionality between concepts. To access this functionality a Protégé plugin can be used. HermiT is an open source reasoner based on the "hypertableau" calculus. It is developed by the University of Oxford. Owlready2 is a package for ontology oriented programming in Python. It can load OWL 2.0 ontologies as Python objects, modify them, save them, and perform reasoning via HermiT (included). Owlready2 allows a transparent access to OWL ontologies (contrary to usual Java based API).

Protégé is a free, open source ontology editor and a knowledge base framework, which can use DL reasoners offering DIG Interface as a back end for consistency checks. , an OWL browser/editor that takes the standard web browser as the basic UI paradigm.

, a standardized XML interface to DLs systems developed by the DL Implementation Group (DIG). , a Java interface and implementation for the Web Ontology Language, used to represent Semantic Web ontologies.