Multi-Agent Systems for Information Retrieval on the World Wide Web

Diplomarbeit von Michael Bleyer

Abstract:

This Diploma thesis describes the implementation of a prototype multi-agent system. The system consists of four different types of agents and is based on the Java Agent Template, an agent framework freely available from Stanford University.

The purpose of the multi-agent system is to aid users in searching and retrieving information available on the WorldWideWeb. Information is categorized in concepts and the different agent share and exchange the knowledge about concepts and documents on the WWW that matches these concepts.

This thesis presents how the information is modeled and how it is communicated between the agents of the system. It also includes prototypes of the agents that demonstrate a working implementation of the approach.

Table of Contents:

1.	Introduction	8
2.	Information Retrieval on the WorldWideWeb	10
2.1	The structure of information	11
2.2	The meaning of information	12
2.3	Locating information	13
2.4	The nature of a search query	15
2.5	Information gathering and query	16
2.6	Conclusion	17
3.	The agent paradigm	18
3.1	An agent from the userÕs point of view	19
3.2	Agent properties	20
3.2.1	Environment	20
3.2.2	Intelligence	21
3.2.3	Learning	22
3.2.4	Autonomy	22
3.2.5	Communication	22
3.2.6	Multi-agent systems	23
3.2.7	Mobility	24
3.3	Conclusion	24
4.	The CEMAS information model	25
4.1	Definition of user and search	25
4.2	The concept architecture	26
4.2.1	Definition of a link	26
4.2.2	Definition of a concept	27
4.2.3	The concept tree	30
5.	The CEMAS agent architecture	33
5.1	The Knowledge Query and Manipulation Language	34
5.2	The Java Agent Template (JAT)	37
5.2.1	JAT knowledge	37
5.2.2	JAT communication	38
5.3	CEMAS agents	41
5.3.1	CEMAS knowledge	42
5.3.2	CEMAS communication	43
5.3.3	The ConceptBroker agent	46
5.3.4	The ConceptServer agent	48
5.3.5	The ConceptClient agent	49
5.3.6	The ConceptSearch agent	51
6.	Example	53
6.1	Example concept tree	53
6.2	Example session	54
6.2.1	Example ConceptClient session	55
6.2.2	Example ConceptSearch Session	60
7.	Implementation	64
7.1	JAT agent overview	64
7.2	JAT messaging	67
7.3	Package agent	69
7.4	Package context	72
7.5	Package resource	73
7.5.1	Resource types	75
7.5.2	ConceptFile class	78
7.6	ConceptUtil package	79
8.	Discussion	80
8.1	The agent paradigm	80
8.2	The concept model	81
8.3	Implementation	83
8.3.1	Communication	83
8.3.2	ConceptBroker	83
8.3.3	ConceptServer	83
8.3.4	ConceptClient	84
8.3.5	ConceptSearch	85
8.4	Conclusion	86
9.	Bibliography	87
	Appendix A	90
	Appendix B	91
	Appendix C	92
	Appendix D	95
	Appendix E	96