Realizing Continuous and Transparent Service Using Agents

Abstract

Many peoples are using the Internet and many types of devices have emarged. In this situation, a single user wants to continue to work in anytime and anywhere. Current contents service targets specific devices, so that it cannot support many different types of devices. To realize continuous and transparent services, we propose a new model of ASP. In our proposed model, User Agent and Application Agent can work together to provide service continuity and device transparency. Then, we implemented a prototype based on this model and evaluated our model. As a conclution, our model could provide continuous and device transparent service. 1

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Realizing Continuous and Transparent Service Using Agents
Takeshi Okuda
Graduate School of Information Science, Nara Institute of Science and Technology
Makoto Takano
Graduate School of Engineering Science, Osaka University
Koichi Tajima
NS Solutions Corporation
Shinji Shimojo
Cybermedia Center, Osaka University
Suguru Yamaguchi
Graduate School of Information Science, Nara Institute of Science and Technology
Hideo Miyahara
Graduate School of Engineering Science, Osaka University
Abstract
Many peoples are using the Internet and many types of de-
vices have emarged. In this situation, a single user wants to
continue to work in anytime and anywhere. Current contents
service targets specific devices, so that it cannot support many
different types of devices. To realize continuous and transpar-
ent services, we propose a new model of ASP. In ourproposed
model, User Agent and Application Agent can work together
to provide service continuity and device transparency. Then,
we implemented a prototype based on this model and eval-
uated our model. As a conclution, our model could provide
continuous and device transparent service.
1Introduction
A broadband Internet access is provided in many areas and
high quality streaming contents such as movies can be ac-
cessed without difficulty. The number of people, who are
watchingstreamingservices, increases avarietyofdevice con-
nected to the Internet. One user may use two or more de-
vices toview contents. Insuch environment,contentsprovider
should make contents in various formats according to the de-
vices. Recently, to ease this situation, Application Service
Providers (ASP), such as Akamai [1] and SmartStream [2] are
working intermediate between contents providers and users.
However, if you are watching streaming video with your PC
and disconnect it, then you try to re-connect to that service
fromanotherdevice, youcannotcontinuefromthatpoint. This
problemisderivedfromthattheinformationabouttheservices
and users are stored in a user’s device or a Database (DB) of
ASP. In case these devices are different in platform, the situa-
tion is more complicated.
To solve these problems, we introduced two concepts of
service continuity and device transparency. We made new
framework for ASP to provide service continuity and device
transparency.
In this paper, we introduce the contepts of service conti-
nuity and device transparency. Next, we explain the model of
ASP to clarify the current problem. Finally, we implement the
prototype of our proposed architecture and evaluate it’s use-
fulness.
2Service Continuity and Device
Transparency
In our research, we defined the concepts of service continuity
and device transparency. The service coninuity is an ability
to continue the services from the previous end point. An ex-
ample of this service continuity is as follows: first, a user is
watching some contents like streaming service, then, he/she
suspends the service, next, he/she resumes the streaming ser-
vice from the point that he/she previously suspended. Many
ASPs provide application framework thatsupportservice con-
tinuity, such as CGI, DB, session management and cookies.
The device transparency is an ability to give the contents
of a service which is suitable for the user’s device. For exam-
ple, one can make use of the service from any type of devices,
such as PC and PDA. Many researches have been made on
device transparency. One of them is contents adaptation, that
transforms Web contents to the format of portable devices [3].
We can use this contents adaptation mechanism as a means
of transcoding the original contents to the format which de-
vice can handle with. Nevertheless, a general architecture of
transcoding a contents suitable to the device is not available.
3Model of ASP
At first, we begin with modeling of currently used ASP. This
model consists of threee components, they are users and ASP
andContentsService Providers(CSP). The CSP providescon-
tentssuchas image, music, videoandsoon. The ASPprovides
applications, on behalf of users and enterprises. The user will
consume the contents using ASP through the Internet.

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The CSP gives their contents to the ASP and asks the ASP
to distribute the contents among their users. The ASP informs
users that new contents are available. Then, users make use
of these contents. A service may be customized to the user
by using a profile about the user which stored in ASP’s DB.
This profile may have user’s name, likes and dislikes, age and
access history (Figure 1).
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Figure 1: The model of ASP
When it comes to service continuity, ASP cannot obtain
the information about user’s usage enough to completely re-
store the service, because the softwares that the user uses and
the applications that ASP provides are not tied up. For exam-
ple, if the user suspends a streaming movie, ASP cannot tell
where the user is watching, so that the user cannot resume the
contents from where he/she was watching.
Furthermore, a single user may access the contents from
multiple devices, such as PC and PDA. In this case, contents
should be adapted to the device which the user is currently us-
ing. Resuming the service by using different device requires
service continuity and device transparency at one time. The
information about the deivces are required to adapt the con-
tents to the device. Many technologies of transcoding from
the Web contents to the specific format have been developed,
but they don’t provide general mechanism. To adapt the con-
tents to any devices, we should know what types of the de-
vice user using and it’s capability. One solution to this prob-
lem is CC/PPproposed by W3C [4]. This framework provides
general-purpose description of device capacity, but it doesn’t
providewholeframework ofgetting device capacity, tarnscod-
ingthe contentsbased on acquired informationand gettingthe
information about the user’s preferrence.
In thenext section, we proposea new modelof ASP which
can providethe service continuityand thedevice transparency.
4Proposed Model
Our proposed model can provide the following features.
1. resume service from the previous end point
2. compensate a device profile to give contents adaptation
mechanism a CC/PP description
This model has three components of Client, User Agent and
Application Agent (Figure 2). In the following, we explain
how to provide these features using these agents in coopera-
tion.
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Figure 2: The proposed model
4.1Resuming a Service
To realize service continuity, the infomation about the usage
of service should not exist in DB or user’s deivce. We decided
that an agent of user have that information on the network.
This agent acts forthe user and resides on the network, and in-
termediate between user and server. We call this type of agent
as User Agent. The User Agentis created for each user. In this
model,a personalUser Agentcan provide onetooneservice to
theuser. Then, we regarda server processandcontentsadapta-
tion mechanism as an application agent that provides adapted
contents of service. These User Agent and Application Agent
work together to make a service continuous and transparent.
The User Agent has four functions: 1) work as protocol proxy
to record the request and return the adapted contents to the
client, 2) manage user and serivce profile to make the cus-
tomized service to the user, 3) watching status of service to
compensate the service, and 4) start service from previous end
point. The Application Agent can provide adapted contents to
the client device based on passed CC/PP description and no-
tify User Agent of the event, to which User Agent subscribed
beforehand.
In normal operation, a client can get the contents in the
contents server by using a User Agent as HTTP proxy. The
User Agent stores the request and it’s contents to the Applica-
tion Profile. In resuming the service, when the client connects
the ASP, User Agent shows the previouscontents to the client.
If the content is streaming media, the User Agent can de-
tect a disconnection of the client, so that User Agent can re-
quest the contents server to return the streaming media from
the disconnected point(Figure 3).
4.2Device Profile Compensasion
We decided to use CC/PP architecture as a contents adaptation
mechanism. To adapt the contents to the device, we have to
know the capability of the device. But, today’s browsers does
not have ability to provide it’s capability to contents server.

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Figure 3: Resuming service
That is whyUser Agent have an ability toprovidea CC/PPde-
scription to contents adaptation mechanism. The User Agent
can handle CC/PP over HTTP. If the client device does not
understand CC/PP, the client can request the contents using
HTTP. Then the User Agent guesses the ability of the client
based on the information of HTTP request header and make
CC/PP description. If the client device is PC, it is not a big
problem, because we can make Web browser plugins to sup-
portCC/PPover HTTP. IftheclientisPDA, thereisnowayfor
the client to provide CC/PP description tothe contentsadapta-
tion mechanism. In our model, the User Agent has knowledge
about the informationof device specific HTTP request header.
When a client requests a content by HTTP, the User Agent
searches its knowledge based on the HTTP request header.
Then the User Agent gets a CC/PP description aboutthe client
device and sends the CC/PP description to the contents adap-
tation mechanism. The contents adaptation mechanism gets
the original contents from the contents server and transcodes
it to the format which the clien device can handle (Figure 4).
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Figure 4: Device Profile compensation
5Evaluation of Proposed Model
To evaluate our proposed model, we implemented the proto-
type based on the proposed model. In this section, we will
explain ourimplementationof prototype and evaluate this sys-
tem in comparison with existing systems.
5.1Implementation
We used mobile agent framework Jumon [5] to implement our
model. Taking future extensions into account, a User Agent
will be able to move not only around the servers of ASP, but
also to a user’s device. This Jumon Agent is a pure Java agent
framework and its class file is very small in size. A User
Agent holds user’s profile and user’s current device’s profile,
and it can communicate with an Application Agent. Applica-
tion Agent can adapt Web contents to the device, using CC/PP
over HTTP to negotiate device capability and user preference.
Once user is disconnected from a service, a User Agent keeps
on watching the service. If Application Agent notifies user
agent of some event, such as home run in a baseball game,
User Agent requests the Application Agent to give a snapshot
of the contents or records it for later reference. When user re-
connect to the service, user agent shows the progress of the
service. In this way, user can keep track on the service, and
can continue to get the service, even if a device is changed.
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Figure 5: An implementation overview
The figure 5 shows the overview of our implementation.
In this figure, two new components can be seen. The Login
Server authenticates the user and create a User Agent for that
user. The Data Broker administers the Device Profile Reposi-
tory and User Profile Repository, which have CC/PP descrip-
tion database and user profile respectively. When User Agent
makes CC/PP description, it guesses the device capability by
searching Device Profile Repository and merges it’s response
with client’s CC/PP description.
We used PCs and PDAs(Sony’s CLIE) as client devices
and PCs for servers. We made the contents service of a base-
ball game. This scenario goes as follows:
1. A user logsin to the ASP using PC and watches stream-
ing video of a baseball game.
2. The user logs out from the ASP. The User Agent sub-
scribes to the specific events to the Application Agent.
3. The user re-connect the ASP using PDA. At this time,
the user can only view the scoreboard (Figure 6).

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4. The user logs out from the ASP again and reconnect
the ASP using PC. At this time, the user can watch the
digest movie of the game (Figure 7).
Figure 6: A screen shot of PDA
Figure 7: A screen shot of PC
5.2Evaluation
In existing systems, continuous services are provided using
cookies and CGI. This system has information about the user
and the sessions. That is why, if a session closed, no use-
ful information about the ongoing service is available. Our
prototype can provide more information about the device and
service status, so that the user can continue the service beyond
the types of devices.
6 Conclusions
We proposed a new model of realizing continuous and trans-
parent services. We adopted existingcontents adaptationtech-
nology to keep service continuity and device transparency. In
this model, a User Agent and an Application Agent work to-
gether to compensate mutual information. We implemented
ourmodelusingmobile agenttakingfutureextensions intoac-
count. Now, we are planning to develop the next genereation
ASP platform.
Acknowledgement
This research was supported in part by “Research for the Fu-
ture” Program of Japan Society for the Promotion of Science
under the Project Advanced Multimedia Content Processing
(Project No.JSPS-RFTF97P00501) and by “Research for the
ASP platform for multiple terminals” of Telecommunications
Advancement Organization of Japan.
References
[1] AkamaiTechnologies, Inc., “Akamai: DeliveringA Better
Internet.” http://www.akami.com/.
[2] NTT SmartConnect, “SmartSTREAM.” http://www.
nttsmc.com/stream/index.html.
[3] K. Harumoto, T. Nakano, S. Shimojo, and S. Nishio, “A
WWW Server with Media Scaling Mechanism Based on
Page Transmission Latency,” in Proceedings of IEEE Pa-
cific Rim Conference on Communications, Computers and
Signal Processing (PACRIM1999), pp. 444 – 447, 1999.
[4] W3C,“CompositeCapability/Preference Profiles(CC/PP)
: A user side framework for content negotiation.”
http://www.w3.org/TR/NOTE-CCPP/.
[5] OMRON Software Co., Ltd., “Jumon Agent.”
http://www.e-jumon.com/.