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A Semantic Web Primer - Chapter 4

Web Ontology Language: OWL Expressivity RDF và RDF Schema mà chúng tôi mô tả trong chương trước là cố ý rất hạn chế: RDF là (khoảng) giới hạn các vị mặt đất nhị phân, và RDF Schema là (khoảng) giới hạn trong một hệ thống phân cấp phân lớp và hệ thống phân cấp một tài sản, với tên miền và phạm vi định nghĩa của các đặc tính này. Tuy nhiên, Nhóm làm việc của Web Ontology W3C1 xác định một số trường hợp đặc điểm sử dụng Semantic Web sẽ yêu cầu biểu cảm hơn nhiều so với. | TLFeBOOK 4 __ Web Ontology Language OWL 4.1 Introduction The expressivity of RDF and RDF Schema that we described in the previous chapter is deliberately very limited RDF is roughly limited to binary ground predicates and RDF Schema is roughly limited to a subclass hierarchy and a property hierarchy with domain and range definitions of these properties. However the Web Ontology Working Group of W3C1 2 identified a number of characteristic use-cases for the Semantic Web that would require much more expressiveness than RDF and RDF Schema offer. A number of research groups in both the United States and Europe had already identified the need for a more powerful ontology modeling language. This led to a joint initiative to define a richer language called DAML OIL2 the name is a join of the names of the U.S. proposal DAML-ONT 3 and the European language OIL4 . DAML OIL in turn was taken as the starting point for the W3C Web Ontology Working Group in defining OWL the language that is aimed to be the standardized and broadly accepted ontology language of the Semantic Web. In this chapter we first describe the motivation for OWL in terms of its requirements and its resulting nontrivial relation with RDF Schema. We then describe the various language elements of OWL in some detail. 1. http www.w3.org 2001 sw WebOnt 2. http www.daml.org 2001 03 daml oil-mdex.html 3. http www.daml.org 2000 10 daml-ont.html 4. http www.ontoknowledge.org oil TLFeBOOK TLFeBOOK 110 4 Web Ontology Language OWL 4.1.1 Requirements for Ontology Languages Ontology languages allow users to write explicit formal conceptualizations of domain models. The main requirements are a well-defined syntax efficient reasoning support a formal semantics sufficient expressive power convenience of expression. The importance of a well-defined syntax is clear and known from the area of programming languages it is a necessary condition for machine-processing of information. All the languages we have .