Description logic

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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

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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

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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.

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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

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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 n Female
• This means that Woman is defined as a female
  person

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Abox

• The ABox contains extensional knowledge about the
  domain of interest. This is assertions about
  individuals, usually called membership assertions
  
• Female n 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

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Brachmans levels

• Conseptual Level
• Actual primitives in the representation
• Constants
• Person
• Female
• Male
• Ect.
• Relationship
• Roles

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Brachmans 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)

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Brachmans 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

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Brachmans 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??)

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Concept
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Implementation
ltDEFCONCEPT NAMEFemalegt ltDEFCONCEPT
NAMEPersongt ltDEFCONCEPT NAMEWomangt
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Implementation
ltDEFCONCEPT NAMEFemalegt ltDEFCONCEPT
NAMEPersongt ltDEFCONCEPT NAMEWomangt ltEQUAL
Cgt ltCONCEPTgt ltPRIMITIVE NAME"Woman"/gt lt/CONCE
PTgt ltCONCEPTgt ltANDgt ltPRIMITIVE
NAME"Female"/gt ltPRIMITIVE NAME"Person"/gt lt/
ANDgt lt/CONCEPTgt lt/EQUALCgt
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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 n Female
• This means that Woman is defined as a female
  person

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FaCT's interpretion
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Concept