(摘录)(book overview)A Semantic Web Primer

Title	A Semantic Web Primer (preface &chapter 1 Introduction)
Publisher	The MIT Press
Year	2004
Author	Grigoris Antoniou and Frank van Harmelen
Level	Introductory
Comment	全书介绍Semantic Web基本概念：XML, RDF, OWL,Rules, Application,Ontology Engineering等； 每章节后的suggested reading列举了很多相关论文，课程，会议等，比较有用。

 

1. Brief Overview

1 The Semantic Web Vision

2 Structured Web Documents in XML

3 Describing Web Resources in RDF

4 Web Ontology Language: OWL

5 Logic and Inference: Rules

6 Applications

7 Ontology Engineering

8 Conclusion and Outlook

App Abstract OWL Syntax

2. Preface

This is an introductory textbook about the Semantic Web.

Its main use will be to serve as the basis for university courses about the Semantic Web.

We concentrate on the main ideas and techniques and provide enough detail to enable readers to engage with the material constructively and to build applications of their own.

3. The Semantic Vision

(1) Knowledge Management

• Knowledge will be organized in conceptual spaces according to its meaning.

• Automated tools will support maintenance by checking for inconsistencies and extracting new knowledge.

 • Keyword-based search will be replaced by query answering: requested knowledge will be retrieved, extracted, and presented in a human friendly way.

 • Query answering over several documents will be supported.

• Defining who may view certain parts of information (even parts of documents) will be possible.

(2)B2C E-Commerce

Current: programming wrapper, in the form of “shopbot”

Vision:

• Pricing and product information will be extracted correctly, and delivery and privacy policies will be interpreted and compared to the user requirements.

• Additional information about the reputation of online shops will be retrieved from other sources, for example, independent rating agencies or consumer bodies.

• The low-level programming of wrappers will become obsolete.

• More sophisticated shopping agents will be able to conduct automated negotiations, on the buyer’s behalf, with shop agents.

(3) B2B E-Commerce

The greatest economic promise of all online technologies lies in the area of business-to-business (B2B) e-commerce.

EDA->Semantic Web

(4) Personal Agent

Make life easier.

4. Semantic Web Technology

Explicit metadata

data about data (i.e. semantic)

Ontology

T.R. Gruber’s definition, later refined by R. Studer:

An ontology is an explicit and formal specification of a conceptualization.

Typically, an ontology consists of a finite list of terms and the relationships between these terms. The terms denote important concepts (classes of objects) of the domain.

The relationships typically include hierarchies of classes.

Logic

Logic can be used to uncover ontological knowledge that is implicitly given.

An important advantage of logic is that it can provide explanations for conclusions.

Initial approaches work at the level of XML, but in the future rules and proofs will need to be represented at the level of RDF and ontology languages, such as DAML+OIL and OWL.

Agent

• Metadata will be used to identify and extract information from Web sources.

• Ontologies will be used to assist in Web searches, to interpret retrieved information, and to communicate with other agents.

• Logic will be used for processing retrieved information and for drawing conclusions.

Semantic Web versus Artificial Intelligence

It is clear that the SemanticWeb will make extensive use of current AI technology and that advances in that technology will lead to a better Semantic Web. But there is no need to wait until AI reaches a higher level of achievement; current AI technology is already sufficient to go a long way toward realizing the Semantic Web vision.

5. A Layered Approach

Principle in building a layer of the semantic web

In building one layer of the Semantic Web on top of another, two principles should be followed:

• Downward compatibility. Agents fully aware of a layer should also be able to interpret and use information written at lower levels.

For example, agents aware of the semantics of OWL can take full advantage of information written in RDF and RDF Schema.

• Upward partial understanding. On the other hand, agents fully aware of a layer should take at least partial advantage of information at higher levels.

For example, an agent aware only of the RDF and RDF Schema semantics can interpret knowledge written in OWL partly, by disregarding those elements that go beyond RDF and RDF Schema.

6. Summary

• The SemanticWeb is an initiative that aims at improving the current state of the World Wide Web.

• The key idea is the use of machine-processable Web information.

• Key technologies include explicit metadata, ontologies, logic and inferencing, and intelligent agents.

• The development of the Semantic Web proceeds in layers.

7. Suggested Reading

An excellent introductory article, from which, among others, the scenario in section 1.2.4 was adapted.

• T. Berners-Lee, J. Hendler, and O. Lassila. The Semantic Web. Scientific American 284 (May 2001): 34-43.