China09SummerSchool2讲座2描述逻辑导论.pptVIP

课程时间表Schedule  讲座2：描述逻辑导论Lecture 2: Introduction to Description Logics 描述逻辑是什么？ 描述逻辑基本系统 描述逻辑种类 描述逻辑实例 描述逻辑是一类知识表示语言表达应用领域的概念定义（有可以被看作为专业术语知识）Description logics (DL) are a family of knowledge representation languages which can be used to represent the concept definitions of an application domain (known as terminological knowledge) 概念与本体Concepts and Ontologies Philosophical discipline, branch of philosophy that deals with the nature and the organisation of reality. Science of Being (Aristotle, Metaphysics, IV,1) What is being? What are the features common to all beings? Vocabulary and Ontology Controlled vocabulary (Jernst 2003) : a list of controlled terms unambiguous non-redundant definition Ontology: a controlled vocabulary expressed in an ontology representation language (Jernst 2003) In computer science … An ontology is an explicit specification of a conceptualization. [Gruber93] An ontology is a shared understanding of some domain of interest. [Uschold, Gruninger96] There are many definitions a formal specification EXECUTABLE of a conceptualization of a domain COMMUNITY of some part of world that is of interest APPLICATION Defines A common vocabulary of terms Some specification of the meaning of the terms A shared understanding for people and machines Why develop an ontology? To make domain assumptions explicit Easier to change domain assumptions Easier to understand and update legacy data To separate domain knowledge from operational knowledge Re-use domain and operational knowledge separately A community reference for applications To share a consistent understanding of what information means. 本体的主要特征Key features of an Ontology 概念层次性Concept hierarchy, 概念包含关系concept subsumption Why not other alternatives 一阶谓词逻辑 the first-order predicate logic 集合论 set theory 程序语言 programming languages 概念与分类 设定存在一个所有个体（Individual）的集合 一个概念被看成是一个个体的集合（Set of individuals） 定义一个概念就是确定一个分类 概念集合与个体集合是不相交的 个体上的一个二元关系集合被称为一个性质（Property/Role) 描述逻辑 Description Logic Basic Des