WEB ENGINEERING

An Aspect Oriented Approach

Joumana Dargham, Sukaina Al Nasrawi

American University of Beirut,Bliss Street, Beirut, Lebanon

Keywords: Aspect oriented Programming, OOHDM, Web-design.

Abstract: Web-Engineering has become, nowadays, the main research interest for software developers. With the

spreading of use of the World Wide Web and the need for a new category of applications the research

community has shifted its interest toward a new era of applications: web-based applications. To parallel the

fast growth of the technology and the new needs for general/special web-applications, research should be

done to improve the development and standardize it as it is done for non-web applications. Many

development and programming tools were implemented to support web-engineering, however studies at the

design level are still premature. Frameworks, design methodologies and web-based development tools are

at an experimental level and depend on individuals efforts. In this context and considering that overheads for

web-development are obstacles more than new methodologies, we are adopting the aspect-oriented approach

for the development of web-applications.

1 INTRODUCTION

In the past few years, the web based information

systems have become the center of interest of many

researchers and business communities. The main

challenges related to their development appear when

dealing with large complex web applications. They

are powered by distributed software implemented

using a myriad of languages like HTML, XML,

JavaScript, etc. The latter encouraged the researchers

who have had a certain experience with software

engineering to explore the WWW. Keeping in mind

the positive impact that software engineering had on

traditional applications; They proposed a new

approach called Web Engineering. The approach

deals with the establishment and use of scientific,

engineering and management principles, disciplined

and systematic approaches to the successful

development, deployment and maintenance of high

quality web based systems and applications (Ginige,

A, 2002).

Within this context, many efforts have been

add

ressed towards defining design models for web

applications such as the Object Oriented

Hypermedia Design Model (OOHDM) or even

frameworks (Schwabe, D., 2001) to improve

reusability. They all explored the maintainability and

scalability of the web application that may be

simplified by modularizing the web system. The

importance of modularization leads us to the notion

of separation of concerns in Aspect Oriented

Programming or AOP. In this paper, we tend to

apply the concepts of AOP onto the web

environment to benefit from the advantages of

separation of concerns and end up having an aspect

based web design model. Very few works have

presented aspect oriented design solutions although

we know that distributed enterprise applications,

such as web applications, have lots of crosscutting

concerns. This scarcity in AOP approaches,

especially with web applications, highlights the

importance of the new developed approach and

sheds the light on the need for the modularity

provided by AOP in the web domain. We try to

apply the concepts of AOP onto web engineering

and design web applications using aspects in order

to clearly structure the application in terms of

functionalities and to improve reusability in web

applications. In what follows, we will first, in

section 2, review the major characteristics of web

applications including the difficulties that should be

taken into consideration when building web systems.

Then, in section 3, we explore the key concepts of

OOHDM and pinpoint the way it can be used to

move into an aspect oriented design model. Section

4 proposes a new approach that adapts the concepts

of AOP onto web applications. Finally, section 5

concludes the paper by mentioning the future works

and plans.

267

Dargham J. and Al Nasrawi S. (2005).

WEB ENGINEERING - An Aspect Oriented Approach.

In Proceedings of the Seventh International Conference on Enterprise Information Systems, pages 267-270

DOI: 10.5220/0002525302670270

 SciTePress

2 WEB APPLICATION

CHARACTERISTICS

The quality of both Web and traditional applications

is judged according to the application’s reliability,

usability and maintainability. However, unlike many

traditional software vendors, if a new company puts

up a new competitive site of a quality that is higher

than existing websites, customers will almost

immediately shift their business to the new site once

they discover it (Offutt, J. 2002). Usually, when

dealing with traditional applications, users take their

time before shifting to another application however

in the web environment, no loyalty is expected from

any customer. To gain users’ trust in the web

domain, many characteristics that assess the quality

of the application have to be considered These

include: reliability, usability and security in addition

to many other important factors such as:

availability, scalability and maintainability. In the

case of online information systems, the required

quality may be higher than many traditional

information systems (Holck, J, 2001). Despite the

different issues handled in the newly emerging web

approaches such as OOHDM, this quality

requirement must be clearly taken into

consideration.

3 BACKGROUNDS: OOHDM

The Object Oriented Hypermedia Design Model

(OOHDM) uses abstraction and composition

mechanisms in an object oriented framework to, on

one hand, allow concise description of complex

information items, and on the other hand, allow the

specification of complex navigation patterns and

interface transformations (Schwabe, D., 2002). With

OOHDM, we end up having two model levels that

are the conceptual and navigational model. The

conceptual model shows classes and their

relationships specifically related to a domain (Lima,

F., 2002). It is concerned with the application’s

domain semantics instead of the type of users and

tasks. On the other hand, the navigational model in

OOHDM describes the navigational structure of a

hypermedia application in terms of navigational

contexts, which are induced from navigation classes

such as nodes, links and indices (Schwabe, D.,

2002). The navigational model consists of two

schemas that are the navigational class schema and

the navigation context diagram. The former defines

all navigable objects as views over the application

domain while the latter defines the main structuring

primitives for the navigational space: navigation

contexts and links that connect them (Lima, F.,

2002). Note that different navigational models may

be built for the same conceptual schema to express

different views on the same domain. The navigation

contexts which are sets of navigation objects may be

specified as groups of contexts too (Refer to (Lima,

F., 2002) for illustrations and more details). In this

paper, we tend to complement the OOHDM by

providing an aspectual representation of the different

possible navigation contexts through the adaptation

of the concepts of AOP onto web applications. The

conceptual part stays intact and we adopt the same

definition and notation used in OOHDM. The

following section details the newly introduced aspect

oriented approach aimed at structuring the web

application and achieving aspect reusability.

4 ASPECT ORIENTED

NAVIGATIONAL MODEL

For web applications to be successful, the

navigational structure must be carefully defined

(Schwabe, D., 2001). In this paper, we mainly

aspectualize the navigational model of a web

application; An aspect refers to a specific

functionality of the application. Note that any

website has a special purpose to achieve. This

purpose refers to the main functionality of the web

system and it is designated as the Core Aspect (CA)

of the web application. The other functionalities

offered by the web system are called Supporting

Aspects (SA). Therefore, according to this approach,

any web application can be modeled as a set

composed of one core aspect and a number of

supporting aspects that interact with each other in

order to achieve a fully functional web system. This

aspectual decomposition of the web application

leads us to a more structured web design model

which in its turn simplifies maintainability and

scalability since the module where the code must be

altered or added can be easily specified. This has a

positive impact, for example, on the usability of an

online application. Indeed, an easily scalable

application will grow without problems and will

provide new functionalities to its customers making

it more and more usable. Figure 1 models the idea of

dividing the web application into CA and SAs. In

addition, there exist other types of online

applications which have separate profiles and users.

In such applications, a new aspect is introduced and

it is referred to as the Authenticity Aspect (AA). In

this case, the application is modeled as a set of AA,

CA and SAs. We can not access the CA unless the

AA returns correctly. Figure 2 illustrates the usage

of AA.

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Figure 1: Aspect decomposition of a web application.

Figure 2: Aspect decomposition of a web application with

AA.

If we consider a CD store online application

example, The main functionality or the main purpose

of the web application would be to buy CDs. So the

core aspect of the online application is to “Buy

CDs”. However, the same website provides a variety

of options such as viewing the list of available CDs,

sending comments to the webmaster besides many

others. These additional functionalities fall into the

category of SAs. Figure 3 illustrates the idea. Also,

Figure 4 represents a sample aspect model of an

online application with AA such as msn hotmail

application. Note that in figures 3 and 4 we only

include few functions due to scarcity of space.

Figure 3: Aspect model of an online CD store.

Also, we distinguish two different types of SAs,

mainly the static and generic supporting aspects.

This differentiation simplifies the developer’s task

when it comes to updating an online application.

From the

Figure 4: Aspect model of a web application with AA.

SA’s type the developer can limit the changes he/she

needs to perform. In a static aspect, the update is

mostly informational but in dynamic aspects the

update can affect more than one entity and thus

consistency has to considered. For example, if we

were to send an e-mail to the webmaster, an

interaction between the user and the application is

required thus we categorize the “Send Comments”

aspect as a Generic Supporting Aspect (GSA).

However, the “Check Contact Info” SA provides

static information about the website and can thus be

categorized as Static Supporting Aspect (SSA). The

interaction between the different identified aspects

of an application mainly models the navigation

aspect of a web application. Aspects are independent

from each other, however in the CD store example,

the user can view the list of available CDs in order

to buy one. The “View List of available CDs” SA

can lead us to the “Buy CD” CA. The latter will be

studied and detailed in further studies.

5 CONCLUSION AND FUTURE

WORK

In conclusion, by aspectualizing a web application,

we are mainly separating its different concerns. The

designer, when adding a new functionality, can

categorize it, add its corresponding aspect and then

WEB ENGINEERING : An aspect oriented approach

269

weave it into the built application. The light has been

shed on the importance of AOP concepts in web

environment and especially in web engineering. We

plan to categorize these aspects and explore the

common aspects between different web applications

belonging to the same domain such as e-commerce

and implement them.

REFERENCES

Offutt, J., 2002. ”Quality Attributes of Web Software

Applications”. George Mason University. IEEE

Software.

Schwabe, D., Rossi, G., Esmeraldo, L., Lyardet, F., 2001.

“Web Design Frameworks: An approach to improve

reuse in web applications”. Epartmento de

Informatica, Brazil; LIFIA Facultad de Informatica,

Argentina.IEEE

Lima, F., Schwabe, D., 2002. “Exploring Semantic Web

Modeling Approaches for Web Application Design”. .

2nd International Workshop on Web Oriented

Software Technology.

Schwabe, D., Rossi, G., 2002. “The Object Oriented

Hypermedia Design Model”.www.telemedia.puc-

rio.br/oohdm/oohdm.html

Holck, J., Clemmensen, T., 2001. “What makes Web-

development different”, Electronic Proceedings of the

24th Information Systems Research Seminar in

Scandinavia, Ulvik in Hardanger, Norway, 11-14

August.

Ginige, A.,2002. “Web Engineering: Managing the

Complexity of Web Systems Development”. University

of Western Sydney, Australia.

Proceedings of the

14th international conference on Software engineering

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