Towards Application Suitability

for PvC Environments

⋆

Andres Flores

and Macario Polo

Departamento de Ciencias de la Computaci

on, Universidad Nacional del Comahue,

Buenos Aires 1400, 3400 Neuqu

en, Argentina

Escuela Superior de Inform

atica, Universidad de Castilla-La Mancha,

Paseo de la Universidad 4, Ciudad Real, Espa

Abstract. Pervasive Computing Environments should support the feeling of con-

tinuity on user’s daily tasks. This concept relies on the availability of different

resources (in this work that will mean availability of applications). We propose a

framework for a component-based integration process, centred on the concept of

composing/adapting applications at run-time. Central to the problem is the task

of component assessment, at syntactic and semantic levels. Our aim is to apply

metadata-based techniques and a process-oriented simulation which resorts to

well establlished veriﬁcation tools.

1 Introduction

Component-based Software (CBS) refers to the possibility of transparently integrate

off-the-shelf (OTS) components on a new target environment in order to satisfy a given

functionality. Then reusability is one of the main aspects to be supported since com-

ponents are used “as they are found” instead of being modiﬁed [1]. Hence, the need

for reliability on components functionality and components inter-connection. Impor-

tant proposals have been delivered for CBS veriﬁcation and validation [2,3,1], though

much work have to be accomplished yet in this area.

Pervasive Computing Environments (PvCEnv’s) require special considerations on

reliability. As pervasive computing implies computation becoming part of the environ-

ment, speciﬁc and disparate software as well as a variety of heterogeneous computing

devices have to be interrelated to allow access to information from anywhere and at

anytime in a secure manner [4].

The user’s relationship to computation changes from the traditional tasks performed

“on the computer”. Instead, individuals may come to expect certain services facilitated

by the environment, which will aim at providing a feeling of “continuity” in their daily

tasks [5]. Such users do not expect to ﬁnd that the surrounding place is in fact a con-

strained environment [6]. Thus applications should not be set to a ﬁxed collection. Here

we explore the possibility to compose applications ‘on demand’ and maintain their

suitability upon different changes. This could be achieved by a run-time assembly of

applications from disparate OTS components [7], which allow to make adjustments by

⋆

This work is supported by the CyTED project VII-J-RITOS2, the UNCo MPDSbC project

04-E059 and the UCLM MAS project TIC 2003-02737-C02-02.

Flores A. and Polo M. (2005).

Towards Application Suitability for PvC Environments.

In Proceedings of the 3rd International Workshop on Modelling, Simulation, Veriﬁcation and Validation of Enterprise Information Systems, pages 58-62

DOI: 10.5220/0002577400580062

 SciTePress

replacing components to satisfy the computational demands of the user as s/he moves

in a place.

Components interconnection motivates an inter-operability pattern involving the

consideration of different levels of information about the components [8] – e.g. syn-

tactic aspects are undertaken in [9], whereas in [10] the focus is on the semantic level.

Our emphasis is at the semantic level but syntactic aspects are considered as well. Our

approach relates to the concept of Semantic Interoperability and our assumption is that

to deal properly with these semantic aspects it is important the consideration of a for-

mal framework to reason about important aspects of the Component-based Integration

Process. Our work aims to develop a solution to address the problems faced in the

integration process which consider speciﬁc phases like: ‘qualiﬁcation’, ‘adaptation’,

‘assembly’ and ‘integration’. Currently we are focused on the Qualiﬁcation phase, for

which different techniques have been applied in connection to the development of a

Component Assessment procedure.

On a PvCEnv the usual scenario implies users changing from one operational con-

text to another. This may involve to use a different device and expect to continue work-

ing under the same or similar application. Hence, requirements are invariably updated

as well as those resources that need to be accessible. When a required application is

not available or degrades its suitability, the ‘assembly’ could be initiated from a previ-

ously executed selection procedure of proper components. They could be fetched from

a repository or being discovered from a mobile device. In any case evaluation should be

rigorous [7].

2 Component Assessment

Our Assessment Procedure intends to compare behavioural aspects from components

against a given set of requirements. The requirement speciﬁcation is assumed in the

form of a component interface – the necessary set of component services. Thus our ap-

proach, which compares components interfaces, actually evaluates a component against

an expected set of services.

At a syntactic level we evaluate matching on the signature of a service – e.g identi-

ﬁers, parameters, and data types. A preliminary approach was developed on a previous

work [7], which is currently being extended. Additionally, components will be enriched

by adding meta-data – an adaptation mechanism called instrumentation [11]. Meta-

data has been used in several approaches as a technique to make testing easier [1, 12,

13]. Currently we are focusing more on the semantic level of interoperability.

Our ﬁrst concern is to add ‘assertions’ to abstract out the black box functionality

hidden on components. Also, the ‘usage protocol’ that describes the expected order of

invocations for component services, will be included in the form of regular expressions.

This technique has been applied on inter-class testing [14], and also on descriptions for

components [15,10]. We expect to succesfully adapt the idea to our framework.

Suppose, for example, post-conditions on services from two similar components.

They should relate to a similar structure and semantic. Hence, they could be thought

as being one a ‘clone’ of the other. Thus we apply some algorithms based on Abstract

Syntax Trees (AST) from [16], which were originally intended to detect similar pieces

of code (clones) on existing programs. Then compatibility for assertions and the usage

protocol is carried out by generating ASTs.

It is also our intention to incorporate a temporal dimension to our approach. As some

authors have pointed out [17, 18], temporal aspects could also be helpful to achieve

a more accurate integration process. A component can be characterized by the states

it goes through during operation. We plan to explore whether all possible states are

achievable on a component under evaluation with respect to their counterparts as in

the requirement speciﬁcation. We are analysing current languages and tools in order to

develop this aspects of the system.

We have started experimentation on such an approach using a process-oriented de-

scription by using Promela language associated to the SPIN veriﬁcation tool. Thus com-

ponents may include a Promela-based speciﬁcation of their behaviour which can be

used to explore the components possible states on the SPIN tool. Statements about the

expected behaviour can be writte and checked using the language of Propositional Lin-

ear Temporal Logic (PLTL) [19] based query. On a previous work [7] we have applied

PLTL to verify the dynamic aspects of components behaviour.

3 Implementation Alternatives

Well-known platforms as Microsoft .NET and Enterprise Java Beans provide mecha-

nisms to enable meta-data incorporation into components. Information about compo-

nents - its structure and the state of their corresponding instances - can be recovered

at runtime by using Reﬂection on both, Microsoft .NET and Enterprise Java Beans.

Particularly .NET includes the possibility of adding Attributes, which is a special class

intended to provide additional information about some design element as a class, a

module, a method, a ﬁeld, and so on.

In order to put our ideas to test and assess the viability of our approach, we have re-

cently developed a preliminary prototype on .Net. Some functions from the framework

process were implemented, like the Recovery procedure from a Component Reposi-

tory. Also a ﬁrst draft of what could be the Adaptation or Tailoring techniques to be

applied on components were represented. The Assessment procedure was also partially

implemented by considering the interface, assertions and usage protocol matching.

4 Conclusions

The main aim behind this project is to automate a Component-based Integration Process

for PvCEnv’s. We have presented a phased scheme and explained the Component As-

sessment procedure related to the Qualiﬁcation phase. For this we apply metadata-based

techniques in order to address Interoperability at a Semantic level.

We have also discussed some alternatives in order to implement different functions

from the framework process, by the use of well-known platforms like .Net and EJB.

The experience gained from building a simple prototype on .Net has been rewarding

but more experimentation is necessary in order to recognize not only the efﬁciency

level but mainly effectiveness on supporting reliability.

Our work is at a preliminary stage and currently we are exploring different tech-

niques to improve our process on efﬁcacy and reliability. As reliability is our main

concern, selecting appropriate methods, techniques and languages, must be accurately

accomplished. Our next step is related to the accomplishment of the semantic level for

component assessment. We believe the complementary procedure with incorporation of

temporal aspects will be a signiﬁcant step to achieve an adequate deployment.

Acknowledgments

We would like to thank Dr. Juan Carlos Augusto, from School of Computing and Math-

ematics, University of Ulster, Newtownabbey, UK. His participation provides a mean-

ingful complementary view giving accuracy and conﬁdence to the project.

References

1. Cechich, A., Piattini, M., Vallecillo, A.: Component-based Software Quality: Methods and

Techniques. Volume 2693 of LNCS. Springer-Verlag (2003)

2. Weyuker, E.J.: Testing component-based software: A cautionary tale. IEEE Software (1998)

54–59

3. Harrold, M., Liang, D., Sinha, S.: An Approach to Analyzing and Testing Component-based

Systems. In: ICSE’99, 1

Wrkshp on Testing Distr. CBS, Los Angeles, CA., US (1999)

4. Garlan, D., Schmerl, B.: Component-based Software Engineering in Pervasive Computing

Environments. In: Workshop on Component-Based Software Engineering: Component Cer-

tiﬁcation and System Prediction (held during 4

ICSE’01), Toronto, Canada (2001)

5. Wang, Z. and Garlan, D.: Task-Driven Computing. Technical Report CMU-CS-00-

154, Carnegie Mellon University, School of Computer Science (2000) http://reports-

archive.adm.cs.cmu.edu/anon/2000/abstracts/00-154.html.

6. Garlan, D.e.: Software Architecture-based Adaptation for Pervasive Systems. In: ARCS’02.

Volume 2299 of LNCS., Karlsruhe, Germany (2002) 67–82

7. Flores, A., Augusto, J.C., Polo, M., Varea, M.: Towards Context-aware Testing for Semantic

Interoperability on PvC Environments. In: IEEE 17

SMC’04, special session: CRIPUC,

The Hague, Netherlands (2004) 1136–1141

8. Euzenat, J.: Towards a principled approach to Semantic Interoperability. In: Wrkshp on

Ontologies and Inf. Sharing, (IJCAI’01), Seattle, US (2001) 19–25

9. Kon

e, O.: An Interoperability Testing Approach to Wireless Application Protocols. JUCS,

Journal of Universal Computer Science 9 (2003) 1220–1243

10. Pahl, C.: An Ontology for Software Component Matching. In: FASE’03. LNCS 2621, pp.

6-21, Berlin, Germany, Springer-Verlag (2003)

11. Flores, A., Polo, M.: Dynamic Assembly & Integration on Component-based Systems. In:

JIISIC, Madrid, Espa

na (2004) 349–360

12. Cechich, A., Polo, M.: COTS Component Testing through Aspect-based Metadata. In:

Building Quality into Components - Testing and Debugging. Springer-Verlag (2005)

13. Orso, A., Harrold, M., Rosenblum, D.: Component Metadata for Software Engineering

Tasks. In: 2

EDO’00, Springer-Verlag LNCS 1999, pp.129-144, Davis, CA, USA (2000)

14. Kirani, S.: Speciﬁcation and Veriﬁcation of Object-Oriented Programs. PhD thesis, Com-

puter Science, University of Minnesota, Minneapolis, USA (1994)

15. Brada, P.: Towards Automated Component Compatibility Assessment. In: 6

Wrkshp on

Comp-oriented Prog, at ECOOP’01, Budapest, Hungary (2001)

16. Baxter, I., Yahin, A., Moura, L., Sant’Anna, M., Bier, L.: Clone Detection Using Abstract

Syntax Trees. In: ICSM’98, pp. 368-377, Maryland, USA (1998)

17. Chen, H., Finin, T., Joshi, A.: Semantic Web in the Context Broker Architecture. In: 2

IEEE PerCom’04, Orlando, US (2004) 277

18. Ranganathan, A., Campbell, R.: An infrastructure for context-awareness based on ﬁrst order

logic. Personal and Ubiquitous Computing 7 (2003) 353–364

19. et.al., B.B.: Systems and Software Veriﬁcation (Model Checking Techniques and Tools).

Springer-Verlag (1999)