CHAPTER 1 Introduction 1.1 An Overview Information Retrieval (IR) is the technique for finding the required data the user needs based on his/her request. Typically, search engines [8] are IR systems that help users to search the web efficiently. Traditional IR methods searching the web based on keywords. Therefore, don't provide capabilities to grasp the conceptualization in the user query and unable to exploit the semantic knowledge within documents and hence can't give accurate answers to specific questions. Moreover, the very fast growth of the Internet results in an explosion of available information that's led to a difficulty in finding information the user wants and hence, search engines have become a crucial need. While searching World …show more content…
Search engines depending on crawlers to traverse the web for building index [10]. Crawler is an automated program (agent) that searches through the Internet and downloads any web pages that can reach. Generally, crawlers have two types, general purpose crawlers and focused crawlers or special topic crawlers. Focused crawler aims to download only pages related to a specific domain of interest. Therefore, use of focused crawler has become a vital since it fulfills the following characteristic: • Focused crawlers overcome the limitations of general – purpose crawlers. They yield good recall as well as good precision by restricting themselves to limited domains. • Focused crawlers propose a good solution for the web freshness problem [57, 58]. Since updating data related to a one specific domain will be easier than updating whole data related to various domains. Hence, general purpose search engines can no longer satisfy the needs of web users who are searching for specialized information. Accordingly, it will be increasingly important to use a semantic search to offers a good solution for the limitations of general – purpose search …show more content…
‘Explicit’ refers to the fact that all elements of ontology are explicitly defined, whereas ‘formal’ means that the ontology specification is given in a language that comes with a formal syntax and semantics, thus resulting in machine executable and machine interpretable ontology descriptions. Finally, ‘shared’ captures the aspect that ontology is representing consensual knowledge that has been agreed on by a group of people, typically as a result of a social process. A major challenge for the emerging semantic web field is to capture the knowledge required and structure it in a format that can be processed automatically. The goal of designing of the web has been: to be useful not only for human–to–human communication but also machines would be able to participate and help (Berners–Lee, 1998). The major problem for current web is that the most of the information has been designed only for human consumption. There is a huge need to design a web, which has machine – understandable information. Fundamentally, the semantic web is intended to solve communication problems that today's web technology cannot handle. We must improve the ability to locate, sort, classify, and make use of