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A Semantic Web Primer - Chapter 3

Describing Web Resources in RDF XML là một metalanguage phổ quát để xác định đánh dấu. Nó cung cấp một khuôn khổ thống nhất, và một tập hợp các công cụ như phân tích cú pháp, để trao đổi dữ liệu và siêu dữ liệu giữa các ứng dụng. Tuy nhiên, XML không cung cấp bất kỳ phương tiện nói về ngữ nghĩa (ý nghĩa) của dữ liệu. Ví dụ, có là không có ý nghĩa dự định liên quan đến làm tổ của các thẻ, đó là vào mỗi ứng dụng để giải thích làm tổ. Hãy để chúng. | TLFeBOOK 3. Describing Web Resources in RDF 3.1 Introduction XML is a universal metalanguage for defining markup. It provides a uniform framework and a set of tools like parsers for interchange of data and metadata between applications. However XML does not provide any means of talking about the semantics meaning of data. For example there is no intended meaning associated with the nesting of tags it is up to each application to interpret the nesting. Let us illustrate this point using an example. Suppose we want to express the following fact David Billington is a lecturer of Discrete Mathematics. There are various ways of representing this sentence in XML. Three possibilities are course name Discrete Mathematics lecturer David Billington lecturer course lecturer name David Billington teaches Discrete Mathematics teaches lecturer teachingOffering lecturer David Billington lecturer course Discrete Mathematics course teachingOffering TLFeBOOK TLFeBOOK 62 3 Describing Web Resources in RDF Note that the first two formalizations include essentially an opposite nesting although they represent the same information. So there is no standard way of assigning meaning to tag nesting. Although often called a language and we commit this sin ourselves in this book RDF is essentially a data-model. Its basic building block is an object-attribute-value triple called a statement. The preceding sentence about Billington is such a statement. Of course an abstract data model needs a concrete syntax in order to be represented and transmitted and RDF has been given a syntax in XML. As a result it inherits the benefits associated with XML. However it is important to understand that other syntactic representations of RDF not based on XML are also possible XML-based syntax is not a necessary component of the RDF model. RDF is domain-independent in that no assumptions about a particular domain of use are made. It is up to users to define their own terminology in a schema language called RDF .