A VIEW ON THE WEB ENGINEERING NATURE

OF WEB BASED EXPERT SYSTEMS

Ioannis M. Dokas

Universität Paderborn, Fakultät EIM, Fürstenallee 11, D-33102 Paderborn, Germany

Alexandre Alapetite

Risø National Laboratory, Systems Analysis Department 110, P.O. box 49

Frederiksborgvej 399, DK-4000 Roskilde, Denmark

Keywords: Web based expert systems, Web engineering, Development process model, Web accessibility.

Abstract: The Web has become the ubiquitous platform for distributing infor

mation and computer services. The tough

Web competition, the way people and organizations rely on Web applications, and the increasing user

requirements for better services have raised their complexity. Expert systems can be accessed via the Web,

forming a set of Web applications known as Web based expert systems. This paper supports that the Web

engineering and expert systems principals should be combined when developing Web based expert systems.

A development process model will be presented that illustrates, in brief, how these principals can be

combined. Based on this model, a publicly available Web based expert system called Landfill Operation

Management Advisor (LOMA) was developed. In addition, the results of an accessibility evaluation on

LOMA – the first ever reported on Web based expert systems – will be presented. Based on this evaluation

some thoughts on accessibility guidelines specific to Web based expert systems will be reported.

1 INTRODUCTION

In many real-world problems, expert knowledge is

scarce and yet in high demand. Computer programs

that simulate the thought process of human experts

can propagate domain expertise and can provide a

solution to these problems. These programs are

known as expert systems. In brief, expert systems

have a knowledge base and an inference engine. The

acquired knowledge of a specific domain is stored in

the knowledge base. The inference engine is where

the processing of the stored knowledge and the

reasoning of the expert system take place.

The Internet – and the World Wide Web in

part

icular – has become the ubiquitous platform for

distributing data and information. The rapid growth

of the Web and the evolution of the corresponding

technologies “forced” Web applications to evolve as

complex, challenging and multidimensional projects.

That gave birth to a new engineering approach

known as Web engineering (Deshpande et al., 2002).

Expert systems can be accessed via the Web,

rming a set of Web applications known as Web

based expert systems. Recently, has been mentioned

that Web based expert systems can be considered as

Web engineering projects that can be developed by

merging an expert system and a Web site/application

subprojects

(Dokas, 2005). In essence, Web based

expert systems can be formed by the combination of

at least two components; namely an expert system

and a Web site.

There has been a lack of research and of general

ethodology for developing Web based expert

systems (Duan, et al. 2005) and a basic question that

requires an answer is the following: Though which

phases a Web based expert system development

project is progressing, starting from its

conceptualisation and ending when it is released?

This paper is an attempt to answer this question. In

addition, this paper aims to demonstrate the need for

collaborative work among expert systems and Web

engineering practitioners and researchers, on the

development and operation of Web based expert

systems. A development process model will be

280

M. Dokas I. and Alapetite A. (2006).

A VIEW ON THE WEB ENGINEERING NATURE OF WEB BASED EXPERT SYSTEMS.

In Proceedings of the First International Conference on Software and Data Technologies, pages 280-283

DOI: 10.5220/0001310102800283

 SciTePress

presented that reveals the Web engineering nature of

such projects. Based on the presented model, a

publicly available Web based expert system called

Landfill Operation Management Advisor (LOMA)

was developed. Additionally, the results of an

accessibility evaluation on LOMA; the first ever

made on a Web based expert system, will be

presented and some thoughts on accessibility

guidelines specific to Web based expert systems will

be reported.

2 THE PROPOSED

DEVELOPMENT PROCESS

MODEL

Development process models are used for the

description, coordination and management of

necessary activities towards the development,

implementation and release of computer systems.

The proposed development process model is

schematically displayed in Figure 1. It can be used

to help Web based expert system developers to

organize and manage effectively the necessary

activities towards their project completion. Bellow,

each phase of the proposed model will be explained

in detail.

Figure 1: The development process model.

Scope and conceptualization:

Web based expert systems are developed to satisfy a

need that has to do with the delivery of a domain

expertise over the Web. The scope of a Web based

expert system is to satisfy the above-mentioned

need. The general concepts, the necessary

components, the basic working principles and tasks

can be briefly described, forming a conceptual

model.

During LOMA’s conceptualisation phase, the

lack of expertise on landfill operations was realized.

A decision was made to acquire the available

expertise on landfill operational problems and to

propagate it worldwide via a Web based expert

system. High-level restrictions on time and on

expenditures were set. Abstract descriptions of the

system’s components and of the user-system

interactions were made.

Requirements and specifications:

Based on the conceptualization model, a more detail

description of the desired functions of the Web

based expert system should be made leading to a set

of functional requirements. In addition, some desired

characteristics and/or constraints could be revealed.

These are defining the non-functional requirements

of the system. The functional and non-functional

requirements together are defining the Web based

expert system specifications.

In LOMA’s case the initial specifications

included: the overall scope and goal of the Web

based expert system, the target group of users, use

cases describing the Web based expert system

behaviour under various scenarios of user requests,

Risk analysis:

The reason of performing the risk analysis is to

assess the factors that may jeopardize the Web based

expert system development, and to define control

measures and procedures that must be activated

whenever anticipated problems occur during the

development process.

Some of the assessed factors that could

jeopardize LOMA project were the selection of:

improper tools like expert system shells, server

applications, Web editors etc., ineffective

knowledge acquisition techniques, unproductive

development strategy for the Web based expert

system software components. Therefore, additional

specifications were established, which were related

to these issues.

Web Based Expert System Development:

When the preliminary phases reach an acceptable

level of completeness, the development of the Web

based expert systems subcomponents can begin.

These components will include at least an expert

system and a Web site. Based on the specifications,

other computer applications, such as GIS and

database systems, can be developed to enrich the

Web system capabilities. The new challenge behind

Web based expert systems development is to

discover methods and techniques to combine,

coordinate and manage the subcomponents

development in order to save resources and time.

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281

That is why the subcomponents development phases

are interconnected with two-way arrows in Figure 1.

Each subcomponent development team can

perform the requirements analysis, specifications,

and risk analysis processes again, but this time at a

low level, among other necessary development

processes such as design, coding implementation

and testing. When all subcomponents reach an

acceptable operation level, they can be combined to

form a prototype Web based expert system. Using

the prototype system it is possible to check the

degree to which the specifications are fulfilled.

Web Based Expert System Testing:

Before launching the Web based expert system on

the Web, it is necessary to apply testing procedures

to identify the degree to which the entire Web based

expert system is correct and complete, based on the

specifications. Moreover,

the knowledge base and

the reasoning mechanism of the expert system

component must be tested and validated for errors.

The testing of LOMA was conducted in three

phases. The first was to evaluate to which degree the

specifications have been achieved. The second was

to invite the collaborative domain experts to use

LOMA and to point out problems, bugs, errors or

improvement suggestions. The third was to send e-

mail invitation to landfill experts from different

countries to evaluate LOMA.

Version Release and Evolution:

During this phase, it is important to make sure that

the system can be used properly and some non-

functional requirements can be fulfilled. Since the

domain knowledge, the used tools and the

corresponding technologies are evolving, the Web

based expert system must evolve with time, because

progressively it will be less satisfactory to use.

Recently, the need to improve LOMA Web

based expert system in a way that will make it more

accessible to people with disabilities, expert users

under time pressure and to mobile devises has been

identified. Bellow, the accessibility evaluation of

LOMA will be presented; as far as the authors know,

this is the first ever reported for Web based expert

systems. Through LOMA’s accessibility evaluation

process, some thoughts on accessibility guidelines,

specifically for Web based expert systems, have

been raised and will be presented.

3 WEB ACCESSIBILITY

The Web accessibility concept refers to a combined

set of measures, namely, how easily and how

efficiently different types of users may make use of

a given service. Developers can extend the

portability and longevity of their Web based expert

system by using standard formats and accessibility

rules. Additional improvements are expected, such

as on speed and usability. Accessible Web pages

should indeed be faster to navigate and minimize the

mental load. These factors have in turn an indirect

impact on safety.

3.1 LOMA Accessibility Evaluation

The system has been tested on desktop computer,

running various Web browsers, and on a PDA with a

screen of 230×320px (IE 4.01). Accessibility,

HTML and CSS automatic validation tools were first

used to spot some flaws. Then, the conformance

evaluation of LOMA has been made by following

the W3C WAI methodology and its “Checklist of

Checkpoints for Web Content Accessibility

Guidelines 1.0” [http://www.w3.org/TR/WAI-

WEBCONTENT/full-checklist.html]. On 65

checkpoints, 17 were successful, 27 failed and 21

were not applicable.

Some general flaws were identified in various

categories, such as invalid HTML and CSS code,

character encoding issues, non user-friendly and non

permanent addresses (URLs) and client side

programming (JavaScript) problems.

Accessibility specific issues were for instance

important pictures without alternative text,

insufficient colour contrast, pop-up windows, form

fields without explicit labels, undefined acronyms or

abbreviations, etc.

3.2 Accessibility Considerations for

Web Based Expert Systems

Based on the experience of evaluating of LOMA,

some thoughts on accessibility recommendations

specific to Web based expert systems are reported.

The system should inform the user of the number

of steps already done, and an averaged estimation of

the remaining steps. Furthermore, listing the

questions already dealt with can help users in

establishing a good mental model. Even for expert

users, it is important to have self-explanatory

questions: pictures can greatly improve text

descriptions and are quickly understood. Similarly,

a glossary of the words used in the context of the

current expertise is an interesting resource.

Some Web based expert systems can be used for

time critical decisions, for which there should be a

possibility to go directly to the possible solutions

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4 CONCLUSIONS

ranked by probability. Similarly, a mechanism to

mark them as “not applicable” or “unknown” should

be investigated.

In many real life and safety critical circumstances,

there is a need for rapid and effective distribution of

expert knowledge and guidance. Web based expert

systems can be an alternative solution to satisfy that

need. This paper introduced a development process

model for Web based expert systems that shows

the

phases through which a Web based expert system

development project is progressing. In addition, this paper

pointed out that the collaborative work of expert

system, Web engineering practitioners and

researchers is essential in such projects.

In safety critical environments, even more efforts

should be put to ensure robustness. On Image 1, a

list of two advises was designed for large screens

and use a simple carriage return <BR> instead of a

standard list. On a smaller screen, this is rendered as

3 lines, making difficult to isolate the 2 advises.

Using meaningful mark-up helps browsers to ensure

the semantics of the page, even under unexpected

situations. Another robustness issue is due to the

behaviour of some widgets, which are more likely to

show their limitations on small screens. This is for

instance the case with the <SELECT> element in

our tests, which crops the text when it is too long to

fit into the screen, as seen on Image 2. It can be

replaced by a set of radio buttons, or checkboxes.

In an attempt to underline the Web engineering

nature of Web based expert system, an accessibility

evaluation on LOMA has been presented. Based on

LOMA’s accessibility evaluation, some thoughts on

accessibility guidelines specific to Web based expert

systems have been reported. Further work is needed

to validate and test them in different publicly

available Web based expert systems.

Finally, some Web based expert systems use

time limited sessions. Users shall be given sufficient

time, but in safety critical applications, sessions

should be avoided.

ACKNOWLEDGEMENTS

This work is supported by the Fifth European

Framework Programme, within the ADVISES

Research Training Network about “Analysis Design

and Validation of Interactive Safety-critical and

Error-tolerant Systems”. We would like to thank

Henning Boje Andersen, from Risø National

Laboratory, for his comments.

REFERENCES

Image 1: List of items.

Deshpande, Y., Murugesan, S., Ginige, A., Hansen, S.,

Schwabe, D., Gaedke, M., and White, M., B., 2002.

Web engineering. Journal of Web Engineering, 1, 3-

17.

Dokas, I., M., 2005. Developing Web sites for Web based

expert systems: A Web engineering approach. In

Proceedings of the Second International ICSC

Symposium on Information Technologies in

Environmental Engineering (Magdeburg Germany,

September 2005), 202-217, Shaker Verlag.

Duan, Y., Edwards, J., S., and Xu, M., X., 2005. Web-

based expert systems: Benefits and challenges.

Information & Management, 42, 799-811.

Image 2: Content overflow.

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