知识图谱本体与推理

本体 Ontology

从一个例子讲起

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name  rank
Bob   Captain
Sue   Sargent
Mary  Admiral
Joe   Sargent

select ?x { ?x rank “Sargent” }
select ?x { ?x a Person }
select ?x { ?x a MilitaryPerson }

如何进行inference?
Tell the computer some triples it infers more triples + RDFS辅助

=> RDFSchema OWL

OWL (Web Ontology Language)

基本思想:
I state a few OWL axioms;
I load lots of triples;
The system infers lots of new triples.

构建模块:
Classes – 类
Properties – 属性
Individuals – 单个个体，类似于instance

OWL中的假设

  1. Unique Name Assumption 
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    bob a foaf:Person; 
    	foaf:name “Bob”;
    	ex:rank “Captain” .


    sue a foaf:Person; 
    	foaf:name "Sue";
    	ex:rank Sargent .
    Unique Name Assumption = TRUE:
    => bob and sue refer to different individuals in the world

Unique Name Assumption = FALSE:
=> bob and sue may refer to the same individual in the world

OWL使用的假设: Unique Name Assumption = FALSE

  1. Open World or Closed World

Closed World: if I don’t tell it something, assume it’s false, 没提到就是false
Open World: if I don’t tell it something, don’t assume anything I might tell it later that it is true, 没提到可能是对的

Class

owl: Thing 所有的invidual均属于owl:Thing类

Knowledge Graph

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