Mobile-Agent Mediated Place Oriented
Communication
Yasuhiko Kitamura1, Yasuhiro Mawarimichi1, and Shoji Tatsumi1
Department of Information and Communication Engineering
Faculty of Engineering, Osaka City University
3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japanfkitamura, ym, tatsumig@kdel.info.eng.osaka-cu.ac.jp
http://www.kdel.info.eng.osaka-cu.ac.jp/~kitamura/

Abstract. When we communicate with others in a most primitive way

like face-to-face conversation, we normally gather at a common physicalplace. This physical constraint has been recognized as an obstacle against
free communication. To relax this constraint, modern communication
systems like post, telephone, and the Internet have been invented. Now
we are building a free society with no border on the Internet by using
the electronic communication tools to enjoy free communication withpeople all over the world. On the other hand, in this network society,we face many serious problems like spam mail and malicious access to
information resources. We believe that one reason causing these problems
is that current communication technologies neglect roles of physical placein primitive communication. Implicitly, a place de nes who is allowed toenter it and who is not.
In this paper, we propose the Agent Mediated Communicator (AMC)
which creates virtual places for electronic communication on the Internet. Communication on the AMC is mediated by mobile agents and isachieved as interactions among agents and services in a place. When we
start a communication with a person, we send a mobile agent to his/herplace. Before the agent enters the place, it is authenticated and can enter
only when it is allowed. Multiple agents can enter in a single place andthey are visible to others. We can install various communication tools
called services in a place like E-mail, Talk, Chat, BBS, WWW and so on.
To show an example of look and feel of AMC, we developed a prototype
of AMC based on a mobile agent platform IBM Aglets.
Place oriented communication by AMC has the following implications.
{ It gives a simple and clear security model for communication.
{ It gives a platform of communityware where people with a common
interest can communicate with each other to create a community.
{ It gives an information network platform which is easily adaptableto current physical social systems because our physical society canbe viewed as a society consisting of mobile agents.

1 Introduction
When we communicate with others in a most primitive way like face-to-faceconversation, we normally gather at a common physical place. This physicalconstraint has been recognized as an obstacle against free communication. To
relax this constraint, modern communication systems such as post, telephone,and so on have been invented and widespread over the world. By using mail andtelephone, we can easily communicate with people who live in distant places.
Information network technology such as the Internet succeeds in alleviating
the constraint dramatically. We can exchange messages with people on the otherside of the earth in a moment by E-mail and can gather and o er various information from and to the world through the WWW. Now we are building a freesociety with no border on the Internet by using these communication tools to
enjoy free communication with people all over the world.
On the other hand, we face many serious problems in this network society.
We are annoyed with uncomfortable incoming mail called spam or junk maileveryday. Our personal information, which is open to the public on the WWW,
might be used for an unintended purpose by others. Group communication on
a BBS (Bulletin Board System) could be threatened by anonymous malicious
posting. Nowadays it is quite dicult to solve these problems just by appealing
to the network users to keep \netiquette" as social rules.
We believe that one reason causing these problems is that current communication technologies that support our network society neglect roles of physicalplace in primitive communication. In our daily life, when we talk with others, weusually consider the place. We usually greet friends or colleagues in a corridor,
an elevator, and almost everywhere. For a business or research discussion, we
usually do it in a meeting room that is separated from others to avoid interventions. When we talk about private matters, we may use a private room to keep
the talk secret from others. Implicitly, a place de nes who is allowed to enter it
and who is not. A person who is not allowed are refused to enter it, or asked
or forced to be out when he/she has already been there. Hence, we choose anappropriate place depending on the contents or participants of communication.
In this paper, we propose the Agent Mediated Communicator (AMC) which
creates virtual places for electronic communication on computer network. Communication on the AMC is mediated by mobile agents and is achieved as interactions among agents and services in a place. When we start a communication
with a person, we send a mobile agent to his/her place. Before the agent enters
the place, it is authenticated, and can enter it only when it is allowed. Multiple
agents can enter in a common single place and they are visible to others andcan interact with each other. We can install various communication tools called
services in a place. Services such as Chat or BBS are shared by multiple agentsin the place. Place oriented communication supported by AMC has the following
implications.

{ It gives a simple and clear security model for communication.
{ It gives a platform of communityware where people can communicate witheach other to create a virtual community.

{ It gives an information network platform which is easily adaptable to cur-rent physical social systems because our physical society can be viewed as asociety consisting of mobile agents.

In Section 2, we show the basic components of AMC and a prototype implemented by using a mobile agents platform called IBM Aglets. In Section 3, we
discuss the above implications in more detail and conclude in Section 4.

2 Agent Mediated Communicator
2.1 Overview
In Fig. 1, we show an overview of AMC (Agent Mediated Communicator).

Place
Service

Service

Entrance: Agent

Launcher

LauncherFig.1. Overview of AMC.
AMC consists of mobile agents, places, and launchers. An agent is a surrogate
of its user with his/her pro le information and moves from the user's launcher
to designated places.
A place accepts agents and o ers communication services to them. The Entrance is a persistent service and gives authentication to an agent that tries toenter the place. Once the agent is allowed to enter the place, it can invoke or use
service programs like Mail, Talk, BBS, Chat, WWW, and so on, available there.
Multiple agents can enter the same place at the same time. They are visible toothers and can interact with each other.
In AMC, we have two ways to establish communication. For example, here
we show two ways of mailing as shown in Fig. 2. In one-way mailing (Fig. 2(a)),
we send an agent with a message from our launcher to a designated place andpost the message in the Mailbox service. This is similar to the current E-mailsystem except the agent is required to be authenticated to enter the place.
In two-way mailing (Fig. 2(b)), we send an agent from our launcher to a
designated place to invoke the Envelope service there. Then, the Envelope service
creates an Envelope agent with an envelope that moves to our launcher. At
our launcher, the Envelope agent starts an envelope program and we put ourmessage in the envelope. Finally, the agent returns to its home place and posts
our message in its Mailbox.
:Sender’s Agent
Receiver:Envelop Agent
ReceiverPlace
Mailbox

Place
Envelop

Entrance

Mailbox

Entrance

Launcher

Launcher

Message

Message

SenderSender(a)1-way Mailing(b)2-way MailingFig. 2. Two ways of mailing.
Group communication services such as Chat and BBS can be implemented
by using the two-way method because they need a client-server setup for bilateral message exchange. In the place, a service starts a server program that stores
messages. When an agent requests to use the service, the service creates an client
agent that moves to a launcher where the request agent is originated and starts
its client program to read and write messages from and to the server. One advantage of this method is its easiness of version-up of client and server programs
because client programs are transferred by client agents. Another advantage isthe visibility of agents. Because agents are visible to others in the place, they
can recognize not only who writes messages but also who can read them. Hence,
we can use this mechanism to create an active community sharing a common
interest or to monitor malicious inspections from anonymous agents.

2.2 Prototype System
We developed an AMC prototype by using a mobile-agent platform IBM Aglets [3].
At this moment, we have not implemented the authentication mechanism.
A place is managed by a window shown in Fig. 3 with the following functions.

Fig. 3. Place management window.

Administration Directory speci es a directory where the con guration andlogs of services o ered in the place are stored.

Service starts a new service program at the place by specifying the name and
the Java class and clicking the START button.
Visiting Agents lists visiting agents; name, originated address, and service
being o ered at the place.
Available Services lists available services at the place.
Shutdown terminates the place.

In Fig. 3, agent Willy from launcher arnold and agents Henry and Philip fromlauncher caesar are at this place and receives Entrance and TestBBS services.
At the place, a service TestBBS is available. Entrance service is a default andpersistent service, so it is not shown in the list.
A launcher is managed by a window shown in Fig. 4 with the following
functions.

Fig. 4. Launcher management window.

Agent creates an agent with a speci ed name and sends it to a speci ed URL
by clicking the SEND button.
Agent List lists agents being sent from the launcher and at remote places. By

clicking buttons, we can send commands to the agents. \STATUS" shows thecurrent status of service that the agent is o ered. \ PLACE" shows otheragents at the visiting place. \CALL BACK" calls back the agent from theplace and terminates it.
When we send an agent to a place, by default the agent invokes its Entrance
service. The service creates an Entrance agent and sends it back to our launcher
to open a window shown in Fig. 5. Then, we can choose services through thiswindow.
Agents in the visiting place are displayed through a window shown in Fig. 6 byclicking the \PLACE" button of launcher management window. We can interact
with other agents by clicking the following buttons.
TALK starts a talk to the designated agent.
INFORMATION shows the user pro le of the designated agent.
CLOSE closes the window.
Here we show how to use a BBS service at a remote place. First we sendan agent from our launcher to a place where a BBS service is available. Whenit succeeds to enter the place, a window shown in Fig. 5 appears. We choose
TestBBS, then a BBS agent comes from the place to our launcher. It starts
a BBS client program, a window in Fig. 7 opens, and a connection between
the client at our launcher and the server at the remote place is established. By
specifying our name and message in NAME and MESSAGE boxes respectively
and clicking the WRITE button, the message is sent to the BBS service andforwarded to the other connected agents.

Fig. 5. Entrance window.

Fig. 6. Agents at a place.

Fig.7. BBS Service.

3 Implications of Place Oriented Communication
With AMC, we bring back roles of place to electronic communication on computer network and propose \place oriented communication (POC)." POC has
several implications as follows.

3.1 Security

Security in electronic communication is one of important issues [4]. For example,
we build a rewall around our intranet and protect our information resource frommalicious access. However, a rewall controls communication of the whole organization but it is not suitable for a user to exibly control accesses to his/her
own resource individually. Application oriented control such as WWW access
control by password or access con guration le is not easy enough for novice
users. Moreover, if we have to con gure access control for each application individually, it would be tiring and too complex to understand the whole view ofaccess control. The AMC gives a simple and uni ed security model by introducing places into communication. We can control access by allowing an agent toenter the place or not, and all communication service is done through this agent.
Another security problem is how to deal with spam mail. In the current
E-mail system, once our address is open to public, we cannot stop incoming
messages whether they are good or bad. Even we try to complain about uncomfortable messages to the sender, he/she may use a fake address, and what isworse, he/she may pretend to use our familiar address.
As shown in Fig. 2, the AMC mailer can protect us from uncomfortable
incoming messages by two methods. In the one-way mailing method, an agent
with a message is required to be authenticated before it enters the place topost it. We can lter out most of anonymous messages and messages from fakeaddresses by rejecting the agents to enter. In the two-way mailing method, wesend an agent to collect a message from its sender, so the sender can not pretend.
Moreover, by this method, we can control the number of incoming messages bylimiting the number of collection. Hence, we can control incoming messages
depending on the origins and the number of messages that we like to read.

3.2 Communityware

In AMC, an agent is visible to other agents in the same place. This function may
be useful to create a community of people with a common interest, which is amain purpose of building communityware [1]. When we have a special interest
in some topic, we open a place and invite others with the same interest to send
agents to the place. Agents are visible and have pro le information of their users,
so we may have more and better chances to know others and to make friends
with them.
In the place, agents store and exchange information concerning the common
interest. The current WWW technology is suitable for distributing knowledge,
but we believe the AMC helps to collect and accumulate knowledge throughinteractions among agents. For example, we can install a special service for developing a software product like Linux where we need many developers to collaborate. The service provides a testbed and developers send agents with softwaremodules to check whether they work together properly.

3.3 Adaptability to Physical Social System
As the Internet spreads out over the world, we are going to create a network
society with no border. It is said that our social regulation system such as laws
cannot catch up with the advancement of the technology. Here we quote an
example from an article on E-commerce [2].
For example, does clicking Accept using a mouse in New York to download a new Netscape browser constitute a binding contract of adhesion?
If so, where is the contract considered valid { in New York where theclick occurs or in California where the server is located? If a dispute
arises, what state has jurisdiction?
Current electronic contract on the Internet loses the concept of place. In ourphysical world, a contract between two parties are often made through humanagents and one of them may go to an oce of the other party to put his/her
signature on documents. The AMC based on mobile agents can naturally model
this process.
The above problem shows that there is a gap between the physical society
where place has a meaning and the network society where it loses its meaning,and how to narrow this gap will be an important issue. Our solution to thisissue is by an approach from the technology side. We believe that it is better tobuild a network society that is a natural extension of the physical society thanan isolated one. The AMC can help to build such a network society because ourphysical society can be viewed as consisting of places and agents.

4 Conclusion
We proposed the Agent Mediated Communicator (AMC) which is a communication platform consisting of places and mobile agents. We developed a prototype
system by using a mobile-agent platform IBM Aglets. In addition, we mentioned
its implications from security, communityware, and its adaptability to physicalsocial systems.
In this paper, we just proposed initial ideas of place oriented communication
by AMC. Our future work is to add an authentication function to AMC andto develop various services to show its advantages. We also should consider theconnectivity to current communication tools like E-mail, WWW, and so on andincorporate them into the AMC platform.
By incorporating mobile agents, we may introduce another security issues
like kidnapping, analyzing, and converting agents, so we need to study more
about these issues.

Acknowledgement
This work is partly supported by IBM Tokyo Research Institute.

References
1. Toru Ishida (Ed.): Community Computing: Collaboration over Global Information
Networks, John Wiley and Sons (1998)
2. Ajit Kambil: Doing Business in the Wired World, IEEE Computer, 30(5) (1997)
56{613. Danny B. Lange and Mitsuru Oshima: Programming and Deploying Java Mobile
Agents with Aglets, Addison Wesley (1998)
4. Rolf Oppliger: Internet Security: Firewalls and Beyond, Communications of theACM, 40(5) (1997) 92{102