**2. Background**

Before mentioning the Semantic Web, it is useful to describe the development of the Web in a nutshell. Nova Spivack has explained Web 3.0, the latest development of the Web [1]. The first era is Web 1.0 which consist of contents that can rarely be changed, most of which are generated by research institutions and business organizations. The next era, Web 2.0, has contents that can be changed frequently, and most of them come from the users creating and updating their information, such as Weblog (blog), wiki, social networks, etc. Now we are in the era of Web 3.0 and Semantic Web. It focuses on linking the data between computers together and processing them directly by computers.

#### **2.1 Structured, semi-structured, and unstructured data**

In terms of simplicity of data processing by computers, the data can be classified into three types:


#### **2.2 What is the semantic web**

Indeed, the Semantic Web is not all new technology. Tim Berners-Lee, who invented the World Wide Web in 1990 [2], announced the concept of Semantic Web in 2001 in the *Scientific American* article [3]. Semantic Web is an extension of the Web that we currently use in which information is given well-defined meaning. In other words, Semantic Web is a Web of data that can be processed directly or indirectly and "understood" by computers. Steve Bratt, CEO of World Wide Web Consortium (W3C) [4], contrasts the World Wide Web which uses hyperlinks to link various resources between computers connected by the Internet and Semantic Web which uses relationship or "meaning" to link resources or "objects" together.
