CS6010 SNA UNIT I Notes

CS6010 SNA UNIT I Notes

UNIT I    INTRODUCTION                                                                                    

Introduction to Semantic Web: Limitations of current Web - Development of Semantic Web - Emergence of the Social Web - Social Network analysis: Development of Social Network Analysis - Key concepts and measures in network analysis - Electronic sources for network analysis: Electronic discussion networks, Blogs and online communities - Web-based networks - Applications of Social Network Analysis.  

 

1.1 Introduction to Semantic Web

§  The Semantic Web is the application of advanced knowledge technologies to the Web and distributed systems in general.

§  Information that is missing or hard to access for our machines can be made accessible using ontologies.

§  Ontologies are formal, which allows a computer to emulate human ways of reasoning with knowledge.

§ Ontologies carry a social commitment toward using a set of concepts and relationships in an agreedway.

§ The SemanticWeb adds another layer on theWeb architecture that requires agreements to ensure interoperability.

1.2 Limitations of the current Web

§  There is a unusual ability to adapt to the limitations of our information systems.

§  This means adaptation to our primary interface to the vast information that constitutes the Web: the search engine.

§  The following are the four questions that search engines cannot answer at the moment with satisfaction or not at all.

1 What’s wrong with theWeb?

   The questions below are specific. They represent very general categories of search tasks.

   In each of these cases semantic technology would drastically improve the computer’s ability to give more appropriate answers.

   Who is Frank van Harmelen? 

   To answer such a question using theWeb one would go to the search engine and enter the most logical keyword: harmelen. The results returned by Google are shown in Figure 1.a

§  If this question and answer would be parts of a conversation, the dialogue would sound like this:

o   Q: Who is Frank van Harmelen?

o   A: I don’t know but there are over a million documents with the word “harmelen” on them and I found them all really fast (0.31s). Further, you can buy Harmelen at Amazon. Free Delivery on Orders Over 15.

§  From the top ten results only six are related to the Frank van Harmelen we are interested in. The word Harmelen means a number of things. It’s the name of a number of people, including the (unrelated) Frank van Harmelen and Mark van Harmelen. Six of the hits from the top ten are related to the first person, one to the latter. Harmelen is also a small town in the Netherlands (one hit) and the place for a tragic train accident (one hit).

§  The problem is thus that the keyword harmelen is polysemous.

§  The reason is search engines know that users are not likely to look at more than the top ten results. Search engines are thus programmed in such a way that the first page shows a diversity of the most relevant links related to the keyword.

§  This allows the user to quickly realize the ambiguity of the query and to make it more specific.

§  In fact, most of us who are using search engines on a daily basis would expect this confusion to happen and would immediately start with a more specific query such as Frank van Harmelen.

§  Again, what we experience is an ambiguity of our query that we could solve by adding additional terms such as Vrije Universiteit or research. This leads to another problem: our request becomes overspecified.

§  First, it is not guaranteed that every mentioning of Frank van Harmelen is accompanied by any or all of these words.Worse yet, pages about Frank van Harmelen may not even mention him by name.

§  None of our queries would return pages about him where he is only mentioned by his first name for example or as van Harmelen, F. Not even if for the human reader it would be blatantly obvious that the Frank in question could only be Frank van Harmelen.