CONTEXT-AWARE MODEL DRIVEN DEVELOPMENT:

APPLICATIONS TO WEB SERVICES PLATFORM

Slimane Hammoudi

, Samyr Vale

1,2

ESEO – Angers, FRANCE

Stéphane Loiseau

LERIA, Université d’Angers, FRANCE

Keywords: Model Driven Development, Context-aware Application, Model, CPIM, CPSM, Merging.

Abstract: Context-aware applications have been developed since the last decade but until today there has not yet been

a common definition about what context means. One thing everybody agrees on is that applications must be

more adaptable for each user. Context-aware applications aggregate different types of context to be more

personalized and to respond more effectively the user needs. Nevertheless inserting personal context

information into application code inhibits software development productivity and reuse. We propose in this

work the separation of business logic from context properties in different models, as context depends

essentially on a particular environment and user situation. We suggest the use of the Model Driven

Development (MDD) approach to design context-aware applications. Context information as models can

improve reusability and interoperability in contextual applications. We use a context metamodel and suggest

a merging model technique to build CPIM (Contextual Platform Independent Model). By traditional

transformation techniques a CPSM (Contextual Platform Specific Model) can be built from a CPIM. Web

Service is the target platform used on account of its distributed and interoperable characteristics.

1 INTRODUCTION

Context-aware computing is a research theme of

Ubiquitous Computing. The term “ubiquitous” in

Computer Science was first applied by Weiser

(Weiser, 1991). The goal is to adapt systems to

respond to the human needs in a transparent way.

The most relevant researches in ubiquitous

computing focus on user interfaces, context-aware

applications and automatic access in human

activities. Context-aware computing studies the

user-system interaction and how managing context

information can adapt services to offer particular

solutions to each user need. Some works use client

name, address, current user location, IP address or

profiles as context information. A simple example is

a cookie registered by a web site on the user PC with

information about identification, preferences, etc.

In (Dey, 2001), context is defined as: “any

information that can be used to characterize the

situation of an entity. An entity is a person, place or

object that is considered relevant”.

From our point of view context is not only

information about the environment of the user

application but also all information linked to the

users’ characteristics and needs.

Their needs are revealed by their behaviour in

the application (what services they invoked, what

information they requested, etc.). We can also

extend the notion of environment to the activities

that the application achieves by client invocations

and what functionalities are being requested to

answer the users needs.

These needs can change many times, so to just

compose the services by the same domain does not

guarantee an effective solution. For Coutaz (Coutaz

et al., 2005) the two critical processes are to

recognize users’ goals and activities, and to map

these goals and activities adaptively onto the

population of available services and resources.

It is necessary therefore that the context

management creates an environment with the

478

Hammoudi S., Vale S. and Loiseau S. (2007).

CONTEXT-AWARE MODEL DRIVEN DEVELOPMENT: APPLICATIONS TO WEB SERVICES PLATFORM.

In Proceedings of the Third International Conference on Web Information Systems and Technologies - Web Interfaces and Applications, pages 478-481

DOI: 10.5220/0001290804780481

 SciTePress

possible services or functions that could serve a user

in same situation.

The key points are that context could be specific

for each user and for each situation, so it is not

reasonable to put context properties into application

models (business logic). However, context could be

represented as a model which contains context

information.

The OMG has stimulated the use of Model

Driven Architecture-MDA (OMG-MDA, 2001) to

define an approach to software development based

on modelling and techniques of mapping and

transformation to achieve implementation on

specific platforms.

In this paper a PIM with context or CPIM

(Contextual Platform Independent Model) improves

models with context and the CPSM (Contextual

Platform Specific Model) achieves contextualized

execution. We suggest a merging technique as the

most appropriate operation to integrate context

models with application models. Separating these

concerns in different models will provide model and

context reusability and interoperability to application

development.

From another point of view, representing context

by models leads to a design of adaptive systems

through MDD.

This paper is organized as follow. Section 2

briefly recalls and discusses the notion of context

and the domain of context-aware application.

Section 3 introduces our general approach of

context-aware model driven development by

emphasizing a merging operation as a main concept

for the contextualization of MDD. In section 4 we

suggest web services as a target platform to build

context-aware applications. Finally, section 5

concludes this paper and discusses future works.

2 CONTEXT AND

CONTEXT-AWARE

APPLICATIONS

Firstly, we will introduce a non-computational view

about context. For a conversation to make sense, two

or more people have to be talking about the same

issue. This issue is the context of the conversation. If

another person arrives, he or she must have to know

the context of the conversation to be able to talk

about the same issue. If the participants of the

conversation talk about different issues then this

conversation will be only noise without any sense.

The context is the element that provides relevant

information to a conversation.

The idea of context-aware applications is to

provide an effective system response using user

behaviour information and adapt the system to

provide the solution desired.

Building context-aware applications is a real

challenge. Managing context is difficult because

there is no pattern about how to capture context,

abstract its information, model or use it.

So in the current context-aware systems, the

context is usually represented inside the application

model (business logic). The designer takes the user

context provided by some context provider and

integrates it into the application code. One problem

of this approach is that it covers only one kind of

context, while generally context is not something

static and it could change in different situations:

different behaviours, users, devices, environments,

etc.

3 APPLYING CONTEXT IN

MODEL DRIVEN

DEVELOPMENT

The Model Driven Development uses a set of

patterns to create, implement, deploy and reuse

systems by models. This paradigm uses different

layers with different abstraction levels to represent

the application by model. The OMG`s MDA (Model

Driven Architecture) (OMG-MDA, 2001) defines

three principal layers.

- Computational Independent Model (CIM),

without system structure details.

- Platform Independent Model (PIM), without

platform details.

- Platform Specific Model (PSM), specifies

execution platform requirements.

These layers target different levels of

abstraction. The essence of MDA is the

transformation capability of different models (Lopes

et al., 2005). The MDA models are based on a

metamodel that defines the model language and the

metamodels are based on a meta-metamodel. Model

transformations are defined by transformation rules

using transformation languages (Bézivin et al.,

2004).

As said before, usually context-aware

applications combine context characteristics with the

application logic. It augments the level of

complexity of the application, because business

logic is mixed with user context. Another problem

CONTEXT-AWARE MODEL DRIVEN DEVELOPMENT: APPLICATIONS TO WEB SERVICES PLATFORM

479

conformsTo

conformsTo ConformsTo conformsTo

out

CPIM

CPSM

Transformation

SourceMM

ContextMM

 MergingM SourceM ContextM

MergingMM

with this approach is changing the context

characteristics will change all the design of the

application.

In MDA through the use of models we aim to

“disconnect” business logic from a specific domain,

and, by this way, to obtain applications which will

be adaptable to many contexts.

The objective of this work is to improve models

of context independently of the business logic based

on MDA and afterwards provide the integration of

these context models to different applications.

With this approach we identify some benefits. In

one hand the application model could be integrated

in different user contexts and the user context could

be integrated to different application models. In this

case changing context does not affect the business

logic.

3.1 The Context Model Development

and the Merging Process

Mappings and transformations are the heart of MDA

(Bézivin et al. 2004). Building contextual

applications implies that a context model has to be

integrated with an application model.

Mapping and transformations are not fitted to

this task because the objective here is to aggregate

context characteristics with the business logic. To do

this task we propose merging techniques that are

used when different models contain specifications of

different requirements.

In (Bottoni et al. 2006) the authors consider that

the merging operation is more suitable when dealing

with multiple input models to create one output

model.The same work says that model merging is a

multiple model transformation and the semantics of

the source models are preserved in the merge model.

In Figure.1 we can see our proposition of

merging techniques to aggregate context information

with the application model followed by traditional

transformations rules which can be applied to build

platform specific models.

We can also use the mapping techniques

specified in (Lopes et al. 2005) to map Contextual

PIM (CPIM) in others CPIMs and Contextual PSM

(CPSM) in others CPSMs. Mapping rules can also

be used to construct CPSM from CPIM as carried

out for the PIM to PSM transformation.

The context model is completely independent of

the application model. In Figure.1 the Context

Metamodel is built separately from the Source

Application Metamodel.

The Context Metamodel only has to contain the

elements of the context. Both conform to the same

Meta-metamodel, i.e. to be merged they must be

represented in the same formalism. If they are

represented in different formalisms a mapping

operation has to be made to put all input models in

the same formalism.

Figure 1: MDA-based model merging for Context-aware

development.

As presented in (Lopes et al., 2005), mapping

techniques can be used to generate automatically

transformation rules between models, which will be

applied from CPIM to CPSM.

The other metamodels: merging metamodel,

transformation metamodel, and target ones must

obey the same rule.

The Context Model and the Application Model

are the input models to be merged. The merging

model is based on the merging metamodel (which

defines the Semantic of Merging Rules).

After the Merging operation we have as an

output model the Contextual Application Model.

Note that the contextualization could be considered

either in a PIM or PSM model. This could be

achieved also on the platform, e.g. a UML Source

Model (with or without merged context) can be

transformed to a web services platform represented

by a WSDL (W3C-WSDL, 2001) target model

(contextualized or not).

4 APPLICATION TO WEB

SERVICES PLATFORM

Web Services (W3C-WSA, 2004) have been used to

build software applications on account of their

distributed and interoperable properties.

There are some works building context-aware

applications on web services platform. We intend in

a modelling context to provide relevant services by

conceptualizing and structuring context information.

MMM : meta-metamodel MM : metamodel M : model

MMM

WEBIST 2007 - International Conference on Web Information Systems and Technologies

480

In Web Services platform context information

could be modelled as XML Schema.

In this platform the context can be supplied by a

service that accesses the XML context information

using a SOAP (W3C-SOAP, 2001) message.

This web service can also be published in a

UDDI (UDDI, 2002) registry and linked to others

services.

However, as we said before our objective in this

work is showing that separating context properties

from application code improves a best practice in

ubiquitous software development.

This web service can bind user’s identification,

profiles, actions or preferences described in an XML

archive. There are some XML databases and

relational databases that support XML.

The application servlet based on this context

information can invoke other specific services to

provide effective solutions.

The context service can also append the context

information about this user in a repository or

database. This action improves real time reaction by

context information.

5 CONCLUSIONS

The objective of this work is to propose the MDD

approach to develop context-aware applications.

Nowadays, most ubiquitous applications developers

put context information into application code.

This way keeps the application and context

from being reusable. As context is particular of each

user, situation and environment we propose the

separation of the context characteristics from

application code. To do this and to improve reuse

and interoperability we have suggested the Model

Driven Development Approach.

Context can be modelled independently of the

application model and can be integrated with the last

one by merging techniques.

Contextual Platform Independent Model

(CPIM) is a solution proposed to integrate Context

Model and OMG`s MDA PIM. Moreover the CPSM

can be built by transformation from CPIM.

Using this approach the abstraction level can be

increased and different formalisms can be used to

represent context.

The use of traditional transformations can

change the models formalisms and refine each

model. Here we have presented a brief discussion

about context and merging techniques to improve

context in model level.

The web service is a target platform used to

support context implementation. Its interoperability

and distributed characteristics become the best

platform to develop contextual applications. For

future works we suggest the development of a

context model framework to guide the designer in

modelling context and a semantic for merging

operation.

REFERENCES

Dey A. K., Understanding and Using Context, Personal

and Ubiquitous Computing, 2001: 4-7.

Bezivin J, Hammoudi S, Lopes D, Jouault F, An

experiment in Mapping Web Services to

Implementation Platforms, Research Report, RR-

IRIN2004-01, France, 2004.

Bottoni P, Fulvio D’Antoni O, Missikoff M, Towards a

unified view of model mapping and transformation.

EMOI Workshop, 2006. CAISE Conference.

Coutaz J, Crowley J L, Dobson S, Garlan D, Context is

key, ACM, 2005: 49-53.

Lopes D, Hammoudi S, Bézivin J and Jouault F, Mapping

Specification in MDA: From Theory to

Practice, INTEROP-ESA 2005, Geneva, Switzerland,

21–25.

OMG-MDA., Model Driven Architecture (MDA)-

document number ormsc/2001-07-01. (2001)

UDDI. Universal, Description, Discovery and

Integration (UDDI) 3.0, 2002. http://www.uddi.org.

Weiser M. The computer for the 21

century, Scientific

American, 1991. p. 94-104.

W3C-SOAP. Simple Object Access Protocol (SOAP) 1.1,

2001.http://www.w3.org/TR/SOAP.

W3C-WSDL., Web Services Description Language

(WSDL)1.1, 2001.http://www.w3c.org/tr/wsdl.

W3C-WSA. Web Services Architecture (WSA), 2004.

http://www.w3c.org/TR/2004/NOTE-ws-arch-

20040211/.

CONTEXT-AWARE MODEL DRIVEN DEVELOPMENT: APPLICATIONS TO WEB SERVICES PLATFORM

481