《高级Web技术》参考资料：语义Web课件 A Semantic Web Primer_Chapter1 The Semantic Web Vision

Chapter 1 The semantic Web vision Grigoris Antoniou Frank van Harmelen 1 Chapter 1 A Semantic Web Primer

1 Chapter 1 A Semantic Web Primer Chapter 1 The Semantic Web Vision Grigoris Antoniou Frank van Harmelen

Lecture Outline Today's Web 2. The Semantic Web Impact 3. Semantic Web Technologies 4. A Layered Approach Chapter 1 A Semantic Web primer

2 Chapter 1 A Semantic Web Primer Lecture Outline 1. Today’s Web 2. The Semantic Web Impact 3. Semantic Web Technologies 4. A Layered Approach

Today's Web Most of today's Web content is suitable for human consumption Even Web content that is generated automatically from databases is usually presented without the original structural information found in databases Typical Web uses today people's seeking and making use of information, searching for and getting in touch with other people, reviewing catalogs of online stores and ordering products by filling out forms 3 Chapter 1 A Semantic Web primer

3 Chapter 1 A Semantic Web Primer Today’s Web ⚫ Most of today’s Web content is suitable for human consumption – Even Web content that is generated automatically from databases is usually presented without the original structural information found in databases ⚫ Typical Web uses today people’s – seeking and making use of information, searching for and getting in touch with other people, reviewing catalogs of online stores and ordering products by filling out forms

Keyword-Based Search Engines Current Web activities are not particularly well supported by software tools Except for keyword-based search engines(e.g Google, AltaVista, Yahoo) o The Web would not have been the huge success it was, were it not for search engines Chapter 1 A Semantic Web primer

4 Chapter 1 A Semantic Web Primer Keyword-Based Search Engines ⚫ Current Web activities are not particularly well supported by software tools – Except for keyword-based search engines (e.g. Google, AltaVista, Yahoo) ⚫ The Web would not have been the huge success it was, were it not for search engines

Problems of Keyword-Based Search Engines o High recall, low precision ow or no recall o Results are highly sensitive to vocabulary Results are sing le Web pages Human involvement is necessary to interpret and combine results o Results of Web searches are not readily accessible by other software tools 5 Chapter 1 A Semantic Web primer

5 Chapter 1 A Semantic Web Primer Problems of Keyword-Based Search Engines ⚫ High recall, low precision. ⚫ Low or no recall ⚫ Results are highly sensitive to vocabulary ⚫ Results are single Web pages ⚫ Human involvement is necessary to interpret and combine results ⚫ Results of Web searches are not readily accessible by other software tools

The Key Problem of Today's Web o The meaning of Web content is not machine accessible: lack of semantics o It is simply difficult to distinguish the meaning between these two sentences I am a professor of computer science I am a professor of computer science you may think. Well, 6 Chapter 1 A Semantic Web primer

6 Chapter 1 A Semantic Web Primer The Key Problem of Today’s Web ⚫ The meaning of Web content is not machine￾accessible: lack of semantics ⚫ It is simply difficult to distinguish the meaning between these two sentences: I am a professor of computer science. I am a professor of computer science, you may think. Well, . .

The Semantic Web Approach o Represent Web content in a form that is more easily machine-processable o Use intelligent techniques to take advantage of these representations o The semantic Web will gradually evolve out of the existing Web, it is not a competition to the current ww 7 Chapter 1 A Semantic Web primer

7 Chapter 1 A Semantic Web Primer The Semantic Web Approach ⚫ Represent Web content in a form that is more easily machine-processable. ⚫ Use intelligent techniques to take advantage of these representations. ⚫ The Semantic Web will gradually evolve out of the existing Web, it is not a competition to the current WWW

Lecture Outline Todays Web 2. The Semantic Web Impact 3. Semantic Web Technologies 4. A Layered Approach 8 Chapter 1 A Semantic Web primer

8 Chapter 1 A Semantic Web Primer Lecture Outline 1. Today’s Web 2. The Semantic Web Impact 3. Semantic Web Technologies 4. A Layered Approach

The Semantic Web Impact Knowledge Management o Knowledge management concerns itself with acquiring, accessing, and maintaining knowledge within an organization o Key activity of large businesses: internal knowledge as an intellectual asset o It is particularly important for international geographically dispersed organizations e Most information is currently available in a weakl structured form(e.g. text, audio, video 9 Chapter 1 A Semantic Web primer

9 Chapter 1 A Semantic Web Primer The Semantic Web Impact – Knowledge Management ⚫ Knowledge management concerns itself with acquiring, accessing, and maintaining knowledge within an organization ⚫ Key activity of large businesses: internal knowledge as an intellectual asset ⚫ It is particularly important for international, geographically dispersed organizations ⚫ Most information is currently available in a weakly structured form (e.g. text, audio, video)

Limitations of Current Knowledge Management Technologies e Searching information Keyword-based search engines EXtracting information human involvement necessary for browsing, retrieving interpreting, combining Maintaining information inconsistencies in terminology, outdated information ● Viewing information Impossible to define views on Web knowledge 10 Chapter 1 A Semantic Web primer

10 Chapter 1 A Semantic Web Primer Limitations of Current Knowledge Management Technologies ⚫ Searching information – Keyword-based search engines ⚫ Extracting information – human involvement necessary for browsing, retrieving, interpreting, combining ⚫ Maintaining information – inconsistencies in terminology, outdated information. ⚫ Viewing information – Impossible to define views on Web knowledge