MARVIN

Modeling Environments with Ubiquitous Computing

Caio Stein D’Agostini and Patricia Vilain

Departamento de Informtica e Estatstica, Universidade Federal de Santa Catarina

Caixa Postal 476 – 88.040-900, Florianpolis, SC, Brazil

Keywords:

Ubiquitous, pervasive, modeling, context.

Abstract:

When different devices and applications start to work with one another, physical and behavioral aspects from

the environment have to be taken into account when designing a system. It is impractical, if not impossible, to

list all possible devices, applications and new characteristics and behaviors that might emerge as result from

the autonomy of each part from the parts of the system, different data interpretation and self-organization

capability. In order to cope with this difﬁculty, this paper combines the contributions from different works as

a way to improve the modeling process of this type of computational environment.

1 INTRODUCTION

The concept of ubiquitous computing was ﬁrst devel-

oped by Mark Weiser in the year of 1988 (Weiser,

1994). The ideia is making tools invisible to user,

keeping the user’s focus on the task been done and

not on the tool. To make ubiquitous computing pos-

sible, the computers should be integrated into the real

world since the ﬁrst stages of applications develop-

ment. Ubiquitous appllications should be capable to

use information about the current context to adapt

themselves. Those contexts are deﬁned by informa-

tion that, if available, can alter the result of an action.

(Satyanarayanan, 2001) deﬁnes context information

as attributes that, when available, can be used to make

decisions without the need to interrupt the user fre-

quently.

The analysis and design methods and the model-

ing tools currently available are usually insufﬁcient

to construct ubiquitous systems (Ingstrup, 2003).

This results on time consuming ad-hoc developments

(Sheng and Benatallah, 2005). To provide better de-

sign conditions, some aspects that need attention dur-

ing the modeling process are listed: physical and digi-

tal representantion of objects in the environment; rep-

resentation of spatial aspects (size, area, etc); identi-

ﬁcation of the information needed by each service;

capability to model how the system affects the en-

vironment and how the environment affects the sys-

tem; and the identiﬁcation of emergent behavioue and

how to treat it. These items are explained in details in

(D’Agostini, 2007).

The remainder of the paper is organized as fol-

lows. Section 2 shows the proposed model, composed

of several other models. In Section 3, a case study is

presented. Finally, Section 4 highlights our conclu-

sions.

2 MARVIN

This section presents a short description of model pro-

posed. This model is named MARVIn (Portuguese for

’Model for Integrated Real/Virtual Environments’).

The model is not indended to be used by itself, as it

only provides some solutions to cover some speciﬁc

modeling aspects referring to ubiquitous computing

environments.

2.1 ContextUML: The Starting Point

Aiming to solve the problems presented in the previ-

ous section, works from different speciﬁc research ar-

eas were studied. The work that provided the greatest

contribution and a was used as the base for this work

was ContextUML (Sheng and Benatallah, 2005),

which provides a meta-model class diagram capable

of representing the dependency of an application to-

wards an speciﬁc context.

ContextUML explicitly separates the operations

of a service from the service, explicitly identi-

ﬁes different relevant context information by con-

262

Stein D’Agostini C. and Vilain P. (2008).

MARVIN - Modeling Environments with Ubiquitous Computing.

In Proceedings of the Tenth International Conference on Enterprise Information Systems - ISAS, pages 262-265

DOI: 10.5220/0001698502620265

 SciTePress

text objects and binds objects (including services)

to these contexts, throught ContextAwarenessMech-

anisms (Sheng and Benatallah, 2005). This makes

possible, for example, to easily identify two services

that might interfere with the other’s functioning.

However, ContextUML does not covers aspects

such as physical aspects of the system, and some of

its contributions can be further extended with contri-

butions from other research projetc.

2.2 Extending ContextUML: Other

Complementary Works

From (May, 2003), we complemented ContextUML

(Sheng and Benatallah, 2005) with the notion of Tan-

gible Objects. These are objects that have a represen-

tation both on the physical world (its physical object)

and on the virtual/digital world (the application). The

interaction of the Tangible Objects in the system and

with the physical world is done throught the use of

Spatial Diagrams (Ingstrup, 2003). These diagrams

are maps featuring the location of relevant physical

and tangible objects in the environments, areas of cov-

erage (sensors coverage for example), etc.

While (Sheng and Benatallah, 2005) and (May,

2003) deal with the static views of the environment,

the aspects related to the dynamic views of the sys-

tems are left uncovered. These includes time re-

strictions, context evolution and changes on services’

availability, etc. Some contributions to cover the

dynamic aspects of the applications in the environ-

ment come from (Ingstrup, 2003) (Castro et al., 2006)

(Derntl and Hummel, 2005) (Chung and Nixon, 1995)

and (Damasceno et al., 2006). The goal when deal-

ing with the dynamics of the system, is not to model

all the different actions and situations that can be con-

templated for the system. Instead, the designer should

worry about the situations he or she considers that

should not happen. We take this approach because

we do not want to model all the different applications

in the environment, but how they can work togheter

and the results of those interactions.

These solutions are presented in seven steps, but

this does not imply the need to follow the same order-

ing. These steps are to be applied using the contribu-

tions from ContextUML, but considering some mod-

iﬁcations on its metamodel in order to better model

the relation between services and operations. Figure

1 shows this new metamodel. The extensions made to

(Sheng and Benatallah, 2005) are in different color.

Each step presents one or some contribution from

related workd and how they contribute to solve the

limitations from their own solutions. To illustrate

each step, a case study was chosen.

Service

Operation

Message

Part

CAObject CAMechanism

ContextBinding ContextTrigger

ActionContextConstraint

Context

AtomicContext CompositeContext

ContextSource

ContextService

ContextServiceComunity

0..*

0..1

0..*

0..1

1..* 0..*

1..*

0..* 1..*

0..*

0..* 1..*

1..*

0..*

1..*

0..*

Breakdown

PropagationStrategy

Figure 1: MARVIn’s metamodel.

3 CASE STUDY: INSTANT

MESSENGER APPLICATION

This application is supposed to locate the addressee’s

location for a message so it can be forwarded to the

instant messenger client application closer to the user

at the time. By keeping track of the user’s location,

there is no need for the user to log-in and logout of a

client application everytime it moves around the envi-

ronment.

The example application is constructed coordinat-

ing the following type of services available in the en-

vironment: a Client application that acts as an inter-

face to the user; a Message Router capable os storing

a message and forwarding to the addressee once its

location is known; a Locator service capable of pro-

viding a target’s location; and Authenticator service

so user’s can gain access to the other services; an En-

trance service which keeps track of users entering and

leaving the environment.

All this services can are independent (their imple-

mentation) from the others, but they need to share in-

formation among them to work properly. On this sec-

tion the MARVIn’s steps are applied to model how

services and devices inside a research laboratory are

coordinated to provide an instant messenger applica-

tion. Note that the resources originally provided by

ContextUML (Sheng and Benatallah, 2005) are not

illustrated here.

1. Creation of a graph of goals for identiﬁca-

tion of conﬂicting requirements and emergent

behaviours. The instant messenger application

modeled here is supposed to be precise, meaning

that messages sent to a user are supposed to be re-

ceived by the closest computer executing a client

MARVIN - Modeling Environments with Ubiquitous Computing

263

service at the time. But it is also supposed to be

cheap and easy to implement, meaning no expen-

sive or sophisticated sensors and devices are to be

used. Figure 2 shows how these goals relate.

Figure 2: Decomposed objectives to predict the system

behaviour in the presence of other services (D’Agostini,

2007).

2. Identiﬁcation of all the objects (physical or vir-

tual) relevant to the application(s). Besides the

already cited services (client, router, locator, au-

thenticator and entrance), the instant messenger

application needs to know about the devices avail-

able to execute the client application. Those are

the desktop and personal computers. It also need

to know about the users (as real people).

3. Mapping the localization of all relevant ob-

jects. The router service needs information about

the computers’ placement in the room, as well

about the users’ location. These objects are tan-

gible objects, since they are relevant both in the

physical as in the digital world. Figure 3 shows

the mapping of the environment and identiﬁes the

tangible objects.

Figure 3: Map of the environment with the instant messen-

ger application (D’Agostini, 2007).

4. Identiﬁcation of the different contextual infor-

mation The messenger needs to know about lo-

cation, both of the users and the computers. It

also needs to know about the users’ current sta-

tus (logged-in or out), which informs if they are

present at the environment and authorized to use

the available services. Another information is re-

lated to the messages that are exchanged between

users.

5. Grouping of the services and devices based on

their functionalities For this case study there is

only one type of each service (all computers have

the same client application, there is only one au-

thenticator service, etc), but to illustrate this step

it will be considered as if several types of location

and authentication related services where avail-

able, resulting in these scopes:

• Authentication: Authentication service execut-

ing on the computers that uses logs-in and a

biometric device that identiﬁes the users by

their ﬁngerprints.

• Location: Image tracking service, which tracks

the user through a camera and a bluetooth ser-

vice that detects the users’ cell-phones location.

6. Identiﬁcation of possible system’s breakdowns

and strategies to deal with it. The breakdown

and propagation strategy identiﬁed for this ex-

ample are related to the provision of information

about location. Next, Figureetapa6 presentes a

brief description of a use case describing the mes-

sage routing, which depends on the location of the

addressee user.

>>Message Routing

1.Message is sent to a user in the room

2.Router requests the addresse’s location

3.The image tracking service receives the request

3A. The service locates the user (go to 4)

3B. The service can not locate because of poor

lighting conditions - BREAKDOWN - AlternativeLo-

cationProvider Strategy

4. ...

>>AlternativeLocationProvider Strategy

1.The location request is sent again, but for the

user’s cell-phone(bluetooth)

2.Awaits for answer

Figure 4: Decomposed objectives to predict the system

behaviour in the presence of other services (D’Agostini,

2007).

Figure 5 shows the breakdown and the propaga-

tion strategy relating to the service request.

7. Identify the time restrictions needed to ensure

the quality of the treated information and con-

sequently of the provided services. Finally, Fig-

ure 6 shows the dynamics of how one service co-

ordinates with the others and how this process af-

fects or is affected by the contextual information.

ICEIS 2008 - International Conference on Enterprise Information Systems

264

<<ServicoDeContexto>>

ImageTrackingLocator

<<Operation>>

ProvideLocation

<<Message>>

LocationAnswer

<<Service>>

Router

<<Operation>>

RoutMessage

<<Context>>

<<Breakdown>>

InsuficientLightning

<<BreakdownTrigger>>

InsuficientLightningTrigger

<<PropagationStrategy>>

AlternativeLocationProvider

<<ContextBindings>>

ImpreciseLocationBinding

Figure 5: Service request, breakdown and propagation strat-

egy (D’Agostini, 2007).

LoginLogoff

Location

MessageType

ProperInterface

User tries to enter

User moves

Sending messages

Receiving messages

User leaves

User can change

computer or logout

[answer==true]

[usr.move==true && usr.wantsToToLeave==false]

[usr.wantsToLeave==true]

[usr.wantsToLeave==false]

Authenticator

responds

Entrance exibts

answer

Entrance gets id

and requests

authentication

Entrance warns

of exit

[user.wantToEnter==true]

[user.wantToEnter==false]

[answer==true && user.wantToEnter==true]

Figure 6: The relation between the actions and the contex-

tual information (D’Agostini, 2007).

4 CONCLUSIONS

From the works studied in order to write this pro-

posal it is easy to see that, while it is clear that tra-

ditional development techniques do not apply to com-

plex systems built based on distributed applications

and portable devices, there is a lack of development

alternatives.

Even if not presented here, comparisons between

different related works where done in (D’Agostini,

2007). Our proposal contributes by incorporating

contributions from the several of those related works,

covering both static and dinamic aspects of the appli-

cations, without the need for tools other than those

already available for a software designer or program-

mer. The work also focus on modeling the failures

and how to treat them, instead of trying to avoid them,

which is not always pratical.

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