1 / 16

Description logic

Description logic. Logic-based formalisms evolved out of the intuition of that predicate calculus could be used to unambiguously capture fact about the world Non-logic-based representations

stefan
Download Presentation

Description logic

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Description logic • Logic-based formalisms • evolved out of the intuition of that predicate calculus could be used to unambiguously capture fact about the world • Non-logic-based representations • built on more cognitive notions like network structures and rule-based representations derived from experiment on recall from the human memory and human execution of tasks like mathematical puzzles solving

  2. Description logic • A family of knowledge representation languages • Can be used to represent the terminological knowledge of a domain of interest in a structured and formally well-understood way • The name description logic refers to: • concept descriptions used to describe a domain • logic-based semantics which can be given by a translation into first-order predicate logic

  3. Description Logic • Consists of “concepts” and “terminology”. • Concepts refer to the expression of a DL language • Terminology denotes a hierarchical structure built to provide a representation of the domain of interest.

  4. Description Logic • Intensional knowledge • General knowledge about a problem domain • The TBox, which contains intensional knowledge in the form of a terminology, and is built through declarations that describe general properties of concepts • Extensional knowledge • Specific knowledge to a particular problem • The ABox contains extensional knowledge which is knowledge that is specific to the individuals of the domain of discourse

  5. TBox • The basic form of declaration in a TBox is a concept definition. This is the definition of a new concept in terms of other previously defined concepts. • Woman ≡ Person ∩ Female • This means that Woman is defined as a female person

  6. Abox • The ABox contains extensional knowledge about the domain of interest. This is assertions about individuals, usually called membership assertions • Female ∩ Person (ANNA) • This state that ANNA is a female person. Given the definition of a woman one can derive that ANNA is an instance of the concept Woman

  7. Brachman’s levels • Conseptual Level • Actual primitives in the representation • Constants • Person • Female • Male • Ect. • Relationship • Roles

  8. Brachman’s levels • Epistemological Level • Types of knowledge representation primitives • Predicates describing a taxonomy of concepts • Cat (Pet) • Mother (Female, Parent) • Predicates describing properties of concepts • Child (hasPet) • Parent (Person, hasPersonChild) • Parent (Cat, hasCatChild)

  9. Brachman’s levels • Logical properties • Syntax • Constants, predicates and roles • (defconcept Person) • (defconcept Woman (and Female Person)) • (defprimrole hasPersonChild) • Semantics • Conserns the meaning of symbols • Realised through a set of algorithms-the inferense engine(FaCT) • Woman (and Female Person) means that a woman is a female person • The inferense engine infers implicit knowledge • Inferential point of view • If all the information stored in the knowledge base is true then the inferred information is true as well

  10. Brachman’s levels • Implementational Level • Conserns how the representation is implemented • FaCT has a Tell/Ask interface • Knowledge base is implemented in XML for sending/receiving data between client/server in FaCT • Tree structure and inheritanse(graph??)

  11. Concept

  12. Implementation <DEFCONCEPT NAME=”Female”> <DEFCONCEPT NAME=”Person”> <DEFCONCEPT NAME=”Woman”>

  13. Implementation <DEFCONCEPT NAME=”Female”> <DEFCONCEPT NAME=”Person”> <DEFCONCEPT NAME=”Woman”> <EQUALC> <CONCEPT> <PRIMITIVE NAME="Woman"/> </CONCEPT> <CONCEPT> <AND> <PRIMITIVE NAME="Female"/> <PRIMITIVE NAME="Person"/> </AND> </CONCEPT> </EQUALC>

  14. TBox • The basic form of declaration in a TBox is a concept definition. This is the definition of a new concept in terms of other previously defined concepts. • Woman ≡ Person ∩ Female • This means that Woman is defined as a female person

  15. FaCT's interpretion

  16. Concept

More Related