Interactive Integration of Information Agentson the Web
Yasuhiko Kitamura1 , Teruhiro Yamada2 ? , Takashi Kokubo3 ?? , Yasuhiro
Mawarimichi1? ? ? , Taizo Yamamoto2 y , and Toru Ishida3
1

2Osaka City University, Osaka 558-8585, Japankitamura@kdel.info.eng.osaka-cu.ac.jp
http://www.kdel.info.eng.osaka-cu.ac.jp/~kitamura/

Laboratories of Image Information Science and Technology, Japan
3
Kyoto University, Kyoto 606-8501, Japan

World Wide Web contains a vast amount of di erent information stored in a huge number of distributed Web sites. Search engines
and information agents have been developed to facilitate eÆcient information retrieval tasks from the Web. By integrating multiple searchengines and information agents as an interoperable system, we increase
the value of each of them. In conventional collaborative systems, the integration process is designed by system designers and is concealed fromthe end users.
This paper proposes an interactive multiagent-based interface called Multiple Character-agent Interface (MCI) where animated character-agents
interact with each other and with the user for assisting in information
retrieval. By using the MCI, even a novice user can create a team of information agents and can self-customize the agents through the interactions
with them. We here report the architecture of MCI and two prototype
systems based on MCI, Venus and Mars, which is a cooperative multiagent system for information retrieval, and Recommendation Battlers,
which is a competitive multiagent system for information recommendation.
Abstract.

1

Introduction

World Wide Web (WWW) provide a means for disseminating and sharing information on the Internet and has been widely used for doing business, education,
research, advertisement and so on. The amount of information stored on the
Web is increasing day by day, but the more the information is stored, the morediÆcult to nd. Search engines are the most popular tools to nd Web pages.
A search engine returns a list of URLs responding to the query keyword(s) submitted by the user, but it often returns too many URLs, which include a fairnumber of unrelated ones, to be processed by a human user.
? Presently with SANYO Electric, Tokyo 113-8434, Japan.
?? Presently with NTT Docomo, Kanagawa 239-8536, Japan.
? ? ? Presently with NTT Advanced Technology, Kanagaww 210-0007, Japan.
yPresently with NTT West, Osaka 530-6691, Japan.

A number of information agents have been developed to replace or reinforce
search engines [11, 12]. For example, Letizia [14], WebWatcher [10], and WebMate [5] learn the preference or interest of user by monitoring the history of Web
browsing or searching performed by the user, and recommend suitable Web pages
for the user or re ne search keywords. Ahoy! [19] analyzes and lters the output
of general-purpose search engine and returns a domain-speci c output such asindividual's homepages. Fab [2] is an information recommendation system thatincorporates the collaborative ltering method.
Combining or integrating search engines and/or information agents adds
more value to each system. Meta-search engines such as MetaCrawler [18] andSavvySearch [8] integrate the output of multiple search engines and succeed to
improve the performance. BIG [13] is an information agent that intelligently
and eÆciently gathers information from multiple sources considering the tradeo between the quality of information and the constraints like time and cost.
RETSINA [20] consists of three types of reusable agents; interface agents, task
agents, and resource agents. An interface agent interacts with the user to receive
a query from the user and returns results. A task agent solves domain-speci ctasks through exchanging information with other agents. A resource agent provides access to a heterogeneous information source. Other multi-agent based
systems, such as federated system [7], InfoSleuth [3], and LARKS[12], incorporate information brokering or information matchmaking mechanism.
In conventional collaborative systems such as mentioned above, the way tocoordinate information agents or information resources is speci ed by the systemdesigners and concealed from the users. Hence, the users are just allowed tosubmit a query to a xed interface and to receive results from the system, but notallowed to change the combination of information agents nor the collaboration
mechanism.
For example, RETSINA agents are reusable and their interface is open to
the system designers but not to the user, so the user can just get access to thesystem only through the interface agent. In the federated system, the process ofcoordination among agents is speci ed in the ACL (Agent Communication Language) such as KQML [6]. The ACL provides an open interface to information
agents but not to human users because it is diÆcult for a human user to communicate directly with agents using the ACL. Hence, neither system is designed
to provide an open interface to the end user.
Each user has di erent demands or preferences for information retrieval.
Some user may like some search engine and others may not. Hence, rather thanjust a ready-made collaborative system, we would like to have a framework where
we can easily make a team of favorite information agents that work together andcustomize them exibly.
This paper proposes the Multiple Character-agent Interface (MCI) as shownin Fig. 1 where multiple character agents, each of which represents an information
agent that resides at a server, collaborate with each other on a client machine. We
can view a character agent as the head of information agent whose body resides
in a server. The collaborative actions for retrieving information are performed

by character agents on the client machine and displayed to the user. The user
can get direct access to the agents by clicking and talking, so he/she can submit
the request to each agent and can customize the agent's actions. The user canalso make a favorite team of agents by calling them out to the client machine.
The advantages of MCI are as follows. The collaboration process among
information agents is open to the user. The user can understand how the process
goes and what happens in the system including some erroneous or inappropriate
actions caused by an agent. In a conventional collaborative system, the user may
not be able to notice such erroneous actions because the collaboration process
is concealed from the user. In the MCI, the user can not only notice the error,
but also x it by tuning the corresponding agent or by replacing it with otherappropriate agent. Hence, the user can customize the team of information agentsthrough visible interactions with them.

User

Fig. 1.

Overview of Multiple Character-agent Interface.

Andre and Rist propose a similar system employing multiple character-agents [1],but their work mainly emphasize the advantage of multiple characters as a presentation media. Agents in their system reside and perform in a client machine
whereas, in our system, agent's bodies reside independent servers in a distributedmanner and agent's heads interact in a client machine.
Section 2 addresses the architecture and the implementation issues of theMultiple Character-agent Interface. Then, two prototypes that use MCI are introduced. Section 3 describes Venus and Mars which is a cooperative multi-agent
system consisting domain-speci c information agents and a personal agent. In
Section 4, we introduce Recommendation Battlers, a competitive multi-agent
system in which two character-agents competitively recommend restaurant information to the user.
2

Multiple Character-agents Interface

We show the system architecture of Multiple Character-agent Interface in Fig. 2.
MCI consists of multiple character-agents; the body of each agent resides in adi erent server. As an autonomous agent mentioned in [16], each agent recognizes
actions taken by the user or other agents through data from sensors, interprets
the actions, and responds through its actuator. Agent behavior is controlled
by a program written in Q [9], which is an interaction design language being
developed by Kyoto University for linking autonomous agents and humans.
Table 2 shows major sensor and actuator commands of a typical MCI agent.
Other optional commands are available according to the functionality of agent.

Actuator
Controller

Q
interpreter

Actuator

SensorActuator

SensorbufferSensorActuator
Controller
Controller

Q
interpreter

Communication
Serverserver3
SensorActuator

Actuator
Controller

server2

SensorController

SensorbufferPostgreSQL

server1

Internet Explorer
with MS-Agent

Fig. 2.

bufferSensorController

SensorclientQ
interpreter
SensorLinux with Java, Servelet, and Chasen

Architecture of Multiple Character-agents Interface.

Here is an example of the behavior of an MCI agent as speci ed in Q.
((?feel)(!speak "Hello.")(!display_dialogue_box "prompt" :title "May I help you?"))This rule speci es that the agent speaks \Hello." and shows a dialogue box
with \May I help you?" when it is clicked.
((?find "time" :hour $hour)(if (and (>= hour 18) (< hour 6))(!speak "Good Night!"))(if (and (>= hour 6) (< hour 12))(!speak "Good Morning!"))(if (and (>= hour 12) (< hour 18))(!speak "Good Afternoon!")))

Sensor Commands:(?feel)(?hear $utterance [:from agent])(?find $database name :parameterparameter)

Action Commands:(!show agent)(!hide agent)(!speak utterance [:to agent])(!play animation action)(!point direction)(!display dialogue box type [:title
title])(!present url)

The agent checks whether it is clicked.
The agent hears an utterance from otheragents or its user.
The agent get information from the speci ed
database.
The agent appears.
The agent disappears.
The agent utters utterance to other agent.
The agent performs the animated action.
The agent points to the speci ed direction.
The agent shows an dialogue box.

The agent shows a Web page at url on its
browser.
The agent submits keyword to a search engine.
(!search keyword)
Table 1. Major sensor and actuator commands of MCI agent.

This rule speci es as the agent checks the time and then speaks the greetingwords, \Good Morning!," \Good Afternoon!," or \Good Night!" according to
the time.
To make an agent perform a complex behavior, rules are grouped in scenes
as follows.
(scene1((otherwise)(!show)(go scene2)))(scene2((?hear "Hello!")(!speak "Hello!"))((?feel)(!speak "I am itchy.")(go scene3)))(scene3((?feel)(!speak "Please stop it.")(go scene4)))// Scene 1// The agent appears// and goes to Scene 2.
// Scene 2// If the agent hears "Hello,"// he says "Hello."// If the agent is clicked,// he says "I am itchy."// and goes to Scene 3.
// Scene 3// If the agent is clicked,// he says "Please stop it."// and goes to Scene 4.

At the initial scene (Scene 1) the agent appears and moves to Scene 2. At
Scene 2, he says \Hello." if he hears \Hello." If he is clicked, he says \I amitchy." and moves to Scene 3. At Scene 3, as the action is di erent from the one
at Scene 2, he says \Please stop it." if he is clicked.
Information agents, which reside in distributed servers, are integrated throughthe integration of their characters (heads) on a client machine. Once an agent iscalled to the client machine, it begins to interact with the user and other agentsin a plug-and-play fashion.
Character-agents are implemented on the MS-Agent platform and controlled
through Java Applets and Java Scripts running within Internet Explorer. By
using multiple frames as shown in Fig. 3, we can realize multiple charactersthat interact with each other and the user. The MCI consists of a control frame
and multiple agent frames. When the system is initiated, agent manager, user
manager, and dialogue manager are downloaded in the control frame. Agent
manager manages agent frames when agents are invoked or stopped. User manager manages users by using the Cookie mechanism. Dialogue manager controls
the order of utterances in order not to make multiple agents talk at the sametime. For a request of showing an agent, the agent manager downloads character
controller, command receiver and transmitter from the agent server in an agent
frame. Character controller is written in Java Script and controls a character
agent. This corresponds to sensor and actuator modules in Fig. 2. Commandreceiver and transmitter are Java Applets connecting the character (head) andthe server (body).
The user's actions (clicks or utterances) to an agent are sensed through its
sensor applet (character controller) and forwarded to the sensor controller in theagent's server through the command transmitter. Actions taken by other agentsare sensed through the communication server and the command receiver. Actioncommands from the agent's server is forwarded to the character through thecommand receiver and the character controller.

(Java Script)(Applet)(Applet)(Java Script)

Fig. 3.

(Java Script)(Applet)(Java Script)(Applet)(Java Script)

Implementation of Multiple Character-agents Interface.

By adopting the above multiagent architecture, we can easily add or remove
agents on the client machine. This allows a wide a variety of collaborative tasks
for information retrieval to be achieved by making various teams of agents.
Moreover, the failure of one agent does not a ect the other agents seriously, so
the performance of the whole team degrades only locally. While the agents should
be autonomous to a large extent, some actions should be tightly controlled. Tothis end we implemented the dialogue manager that prevents them from speaking
at the same time.
3

Venus and Mars: A Cooperative Multiagent System for
Information Search

Search engines are the most widely used tools for retrieving information fromthe Web. A drawback of conventional search engine is that it tends to return
too many URLs with low precision as the amount of information increases on
the Web. One approach to deal with this drawback is to build domain-speci csearch engines that can deal with some speci c topics with high precision [19].
Furthermore, a platform where such domain-speci c search engines or agentscollaborate with each other looks promising.
Venus and Mars (VandM) [22] is an information retrieval system in which
multiple character-agents work cooperatively to assist the user. As shown in
Fig. 4, VandM consists of three types of character-agents. Kon-san is the information agent that locates Web pages about cooking recipe. When the user
submits a Japanese query that include keywords about recipe, such as \I would
like to eat a pork dish," Kon-san extracts one or more keywords about recipe(\pork") and submit the keyword(s), with keyword spices1 for the recipe domain, to a general-purpose search engine2 . It then receives search results fromthe search engine and shows them to the user through the Web browser. In caseit receives too many results, it automatically asks for additional keywords toreduce the number of results.
Cho-san has knowledge about cooking ingredients and health. Responding
to an utterance that includes keywords related to cooking ingredients or health,
it utters comments about the relations between cooking ingredients and health,such as \Leeks are good for colds."
Pekko is the personal agent; it initially appears on the client machine andcalls other agents. It chats with the user, and monitors the user's search history.
When needed, it suggests some search keywords to Kon-san on behalf of its user
referring to the user's history.
A snapshot of Venus and Mars is shown in Fig. 5. A typical cooking recipe
search is given below.
(1)Pekko: \May I help you?"(2)User: \I would like to eat a pork dish."(3)Kon-san \OK. Let me locate some recipes that use pork. How do you likethis?" (He shows a recipe page on the browser.)1

Keyword spices are domain-speci c keywords to improve the performance ofgeneral-purpose search engine. [15] discusses how to discover keyword spice semiautomatically by using a machine learning technique. For example, tablespoon _(:tablespoon ^ recipe ^ :home ^ :top) _ (:tablespoon ^ :recipe ^ pepper ^ :pan)is discovered for the recipe domain.
2
http://www.goo.ne.jp/

Nickname
Type

Pekko

Kon-sanCho-sanPersonal Agent

Information Agent

Information Agent

Function

Chatting with theuser.
Learning the user’s
user
preference.

Searching WWW
pages concerning
cooking recipes.

Providing comments
about combination of
cooking ingredients andhealth.

Knowledge

User profile
User’sKeywords about
recipes, ingredients,and seasoning.

Database about cooking
ingredients and health.

Fig. 4.

Character-agents in Venus&Mars.

(4)Cho-san \Pork is good for the digestion. It is a good way to get vitamin

B."(5)Kon-san \The number of search results is over 1000. Let me reduce thenumber. What kind of seasoning do you like?"(6)Pekko: \I know Kitamura-san likes Japanese food."(7)Kon-san: \OK. Let me nd some Japanese recipes that use pork. How do

you like this?" (He shows another recipe page on the browser.)(8)Pekko: (Responding to a click from the user) \May I help you?"(9)User: \I want a recipe that is good for recovering from a cold."(10)Kon-san: \?"(11)Cho-san: \Leeks are good for colds."(12)Kon-san: \OK. Let me locate recipes that use leeks. How do you like this?"(He shows a recipe page that mentions leeks on the browser.)

In VandM, agents collaborate with each other in two ways. In the above
dialogue steps, (5) to (7), Pekko assists Kon-san in reducing the number of search
results. In utterance (5), Kon-san asks for a tip on seasoning, Pekko answers \Iknow Kitamura-san likes Japanese food." on behalf of the user by referring to
his interaction history. Of course, if the user does not like Pekko's suggestion,
he/she can correct Pekko's utterance by indicating his true preference directly to
Kon-san through the dialogue box. Pekko recognizes this correction and updates
the user's preferences stored in its database.
In the above dialogue steps, (9) to (12), Cho-san assists Kon-san. In this case,Kon-san cannot answer the request \I want a recipe that is good for recoveringfrom a cold." because it has no knowledge about health. On the other hand,Cho-san has knowledge about cooking ingredients and health, so it makes thecomment \Leeks are good for colds." Kon-san takes the comment as a clue toinitiate a new search with the keyword of leek. This type of collaboration showsa potential of VandM for realizing various type of information search by adding
agents to the team. For example, if we add a restaurant recommendation agent
to the team, the user's request for a recipe with salmon may also result in arecommendation of local restaurants specializing in salmon.

Fig. 5.

4

A snapshot of Venus&Mars.

Recommendation Battlers: A Competitive Multiagent
System for Information Recommendation

With the growth of e-commerce market, a large number of shopping sites areopen on the Internet. Recently comparison shopping sites, such as www.dealtime.com,
are also available. Such a site collects information from multiple shopping sites
and provides a list of commodities sorted in order of the price. Though it is avery convenient tool to nd the cheapest price, it does not provide direct interactions between buyers and sellers. We here propose a framework where an
information user (buyer) and providers (sellers) directly interact with each otherthrough information agents. This scheme gives a new style of e-commerce wheremultiple sales agents directly negotiate with the customer.
Recommendation Battlers(RB)[17] is a multiagent system for information
recommendation in which two character-agents competitively recommend information. It consists of two restaurant recommendation agents; Peedy and Genie.
Responding to a request from the user, Peedy collects relevant restaurant pages

from Yahoo! Gourmet3 and extracts their addresses and average cost. It thencalculate the distance from the nearest station by referring to the addresses.
Genie also do the same process but it uses Kansai Walker4 . The user and agents
interact on a client machine as shown in Fig. 6. A typical dialogue is given below.
(1)User: \I would like totion."nd a good noodle restaurant near Shinsaibashi sta-(2)Genie: (After collecting information from the Kansai Walker) \Do you like

Restaurant A? The average cost is around 2,000 Yen and the distance from
Shinsaibashi station is 90m."(3)User: \I like it."(4)Peedy: (After collecting information from the Yahoo! Gourmet) \Do you
like Restaurant B? The average cost is around 2,500 Yen and the distancefrom Shinsaibashi station is 80m."(5)User: \No, I don't like it."(6)Peedy: \Do you like Restaurant C? The average cost is around 2,200 Yen
and the distance from Shinsaibashi station is 80m."(7)User: \Good."(8)Genie: \I sure that you like Restaurant D. The average cost is around 1500
Yen and the distance from Shinsaibashi station is 70m."(9)Peedy: \I have no more restaurant to recommend."

Fig. 6.

3
4

A snapshot of Recommendation Battlers

http://gourmet.yahoo.co.jp/
http://www.walkerplus.com/kansai/gourmet/

In contrast to VandM, where agents cooperate, agents in RB compete witheach other. Each monitors the other agent's proposals and the user's responses.
It then proposes a new item that is more appropriate given the course of dialogue
estimating the preference of user by using a rational proposal mechanism [17].
For example, in utterance (2), Genie proposes Restaurant A with the average
cost of 2,000 yen and the distance of 90m. After the user accepts the proposal, theopponent Peedy proposes Restaurant B which looks better from his perspective
because the distance is nearer than that of Restaurant A. However, the user does
not accept the proposal, so Peedy proposes another Restaurant C. Throughinteractions with the user, Genie and Peedy continue to propose restaurants
estimating the preference of user until one of them has nothing to propose.
5

Future Study and Conclusion

In this paper, we proposed the MCI where the user performs information retrieval tasks interacting with multiple information agents, and introduced two
prototypes, Venus and Mars and Recommendation Battlers, using the MCI.
Collaborative tasks performed in these prototypes are rather simple and a lotof future work still remains to build more advanced collaborative information
agents.

Capability for collaboration The MCI agents start to collaborate with each otheronce they are called on the client machine in a plug-and-play fashion. Collaborative actions performed by agents in our current prototypes are simple suchas association or extension of search keywords. To realize more advanced collaborative features, we need to incorporate collaborative mechanisms using coordination and negotiation techniques, which have been studied in the eld of
multi-agent systems [21], into our systems.

Capability for presentation In our current prototypes, collaboration among agentsis presented as a conversational activity. Conversation among agents performed
on a computer display is volatile and it may not be suitable for presenting acomplex collaborative activity. Hence, we need to improve the presentation skill,for example, by creating a virtual space where agents can interact with not only
other agents but also virtual objects. Such skills have much concern with thework being done by Andre and her colleagues [1].

Capability for interaction In our current prototypes, agents interact with theuser mainly by using natural language, but just use a simple technique such as
keyword extraction from an utterance in Japanese. Natural language is the mostnatural way of communication for human users, especially for novice users suchas children and old people. For more complex interactions with the user, moreadvanced features of natural language processing are needed to be applied toour agents.
Current Internet-based information systems depend heavily on the Web technology. Since we can put not only text, but also image and audio, on a Web

page, the Web is highly expressive. The XML technology will further enhancethe value of current Web system. On the other hand, the Web information system looks static because it just provide information in a page by page way.
Character agents enhance the Web technology in another way and make it look
more dynamic and interactive. To this end, a number of works have been donein the academic eld [4] and some are commercially used such as Extempo 5 ,Haptek 6 , Virtual Personalities 7 , Arti cial Life 8 and so on. The MCI provides
a framework where multiple character agents are integrated as a collaborative
system. This scheme may lead to a new generation of agent-based information
integration systems after the XML age.
Acknowledgement

This paper reports the progress of a joint project of Kyoto University, Osaka
City University, SANYO Electric, NTT West, and NTT Comware at LIST (Laboratories of Image Information Science and Technology) subsidized by NEDO(New Energy and Industrial Technology Development Organization). I thankMasahiko Kyosaka, Kiyomasa Okumura, Yuji Tomono, Hiroshi Morimoto, Mutsumi Ikeda, and Toshiki Sakamoto for their contribution to the development of
the system.
References

1. Andre, E., Rist, T.: Adding Life-Like Synthetic Characters to the Web. Cooperative
Information Agents IV, Lecture Notes in Arti cial Intelligence 1860. Springer (2000)
1{132. Balabanovic, M., Shoham, Y.: Fab: Content-Based, Collaborative Recommendation.
Communications of the ACM, 40(3) (1997) 66{72
3. Bayardo, R.J., Bohrer, W., Brice, R., Cichocki, A., Fowler, J., Helal, A., Kashyap,
V., Ksiezyk, T., Martin, G., Nodine, M., Rashid, M., Rusinkiewics, M., Shea, R.,
Unnikrishnan, C., Unruh, A., Woelk, D.: InfoSleuth: Agent-Based Semantic Integration of Information in Open and Dynamic Environments. In Proceedings ACM
SIGMOD International Conference on Management of Data (1997) 195{206
4. Cassell, J., Sullivan, J., Prevost, S., Churchill, E. (eds.): Embodied Conversational
Agents. The MIT Press (2000)
5. Chen, L., Sycara, K.: Web Mate: A Personal Agent for Browsing and Searching. In
Proceedings of the Second International Conference on Autonomous Agents (1998)
132{139
6. Finin, T., Labrou, Y., May eld, J.: KQML as an Agent Communication Language.
In Software Agents, AAAI Press (1997) 291{3167. Genesereth M.R.: An Agent-Based Framework for Interoperability. In Software
Agents, AAAI Press (1997) 317-345
5http://www.extempo.com
http://www.haptek.com
7
http://www.vperson.com
8
http://www.arti cial-life.com
6

8. Howe, A.E., Dreilinger, D.: Savvy Search: A Metasearch Engine That Learns WhichSearch Engines to Query. AI Magazine, 18(2) (1997) 19{25
9. Ishida, T.: Interaction Design Language Q: The Initial Proposal. In Proceedings 15th
Annual Conference of Japanese Society for Arti cial Intelligence, 2A2-03 (2001)
10. Joachims, T., Freitag, D., Mitchell, T.: WebWatcher: A Tour Guide for the World
Wide Web. In Proceeding of the 15th Joint Conference on Arti cial Intelligence(1997) 770{77511. Klusch, M.: Intelligent Information Agents, Springer (1999)
12. Klusch, M.: Information Agent Technology for the Internet: A Survey. Journal on
Data and Knowledge Engineering, 36(3) (2001)
13. Lesser, V., Horling, B., Klassner, F., Raja, A., Wagner, T., Zhang, S.X.: BIG: An
agent for resource-bounded information gathering and decision making. Arti cialIntelligence, 118(1-2) (2000) 197{244
14. Lieberman, H.: Letizia: An Agent That Assists Web Browsing. In Proceedings ofthe 14th International Joint Conference on Arti cial Intelligence (1995) 924{929
15. Oyama, S., Kokubo, T., Yamada, T., Kitamura, Y., Ishida, T.: Keyword Spices:
A New Method for Building Domain-Speci c Web Search Engines. In Proceedings
17th International Joint Conference on Arti cial Intelligence (2001) (in press)
16. Russell, S.J., Norvig, P.: Arti cial Intelligence: A Modern Approach. PrenticeHall(1995)
17. Sakamoto, T., Mawarimichi, Y., Kitamura, Y., Tatsumi, S.: Competitive Information Recommendation System Using Multi-Characters Web Information. In Proceedings 15th Annual Conference of Japanese Society for Arti cial Intelligence, 1F101 (2001)
18. Selberg, E., Etzioni, O.: Multi-Service Search and Comparison Using the
MetaCrawler. In Proceedings of the 4th International World Wide Web Conference(1995) 195{208
19. Shakes, J., Langheinrich, M., Etzioni, O.: Dynamic Reference Sifting: A Case Studyin the Homepage Domain. In Proceedings of Sixth International World Wide Web
Conference (1997)
20. Sycara, K., Zeng, D.: Coordination of Multiple Intelligent Software Agents. International Journal of Cooperative Information Systems 5(2&3) (1996) 181{21121. Weiss, G.: Multiagent Systems: A Modern Approach to Distributed Arti cial Intelligence. The MIT Press (1999).
22. Yamada, T., Kokubo, T., Kitamura, Y.: Web Information Integration Using Multiple Character Interface. In Proceedings 15th Annual Conference of Japanese Society
for Arti cial Intelligence, 1F1-05 (2001)