To specify quality requirements for Web 2.0 applications we propose an integrated approach which considers features for contents, functionalities and services. In this work we discuss how to model internal quality, external quality and quality in use views taking into account not only the software characteristics - as those specified in the ISO 9126-1 quality models- but also the own features to Web applications (WebApps). Particularly, we thoroughly discuss the modeling of the content characteristic for evaluating the quality of information - so critical for the whole Web application eras. The resulting models contribute towards a multidimensional integrated approach to evaluate WebApps at different lifecycle stages, independently of Web eras.
As the Web usage continues to grow, users expect
WebApps to be more mature with regard to the
functionalities and contents delivered for their intended
tasks at hand. Moreover users expect these functions and
contents be relevant, accurate, suitable, usable, secure,
personalised, and ultimately with perceived quality.
Despite the major breakthrough in Web methods and
technologies there are some Web Engineering branches
still in their infancy: Modelling of quality requirements at
different lifecycle stages is one of them. In this paper we
propose, based on related research literature and a bunch
of ideas published in [
WebApps were conceived as content-oriented artefacts from the very beginning. Few years later, Websites started to provide not only contents but software-like functionalities and services as well. Since then, WebApps have at a fast pace emerged for many different sectors as e-commerce, e-learning, e-entertainment, and so forth. After that era named Web 1.0, a recent era that considers a set of strategies and technologies focusing on social networking, collaboration, integration, personalization, etc. is emerging – currently called Web 2.0. We argue that WebApps will continue being centered on functionalities, services and contents independently of the new technologies and collaboration strategies. However, as aforementioned a challenging issue still is how to specify and assess the quality and the quality in use of WebApps since their intrinsic nature will continue being both content and function oriented.
In the present work, by reusing and extending the ISO
9126-1 [
The rest of this paper proceeds as follows. In Section 2, we give an overview of the Web eras as well as the unique intrinsic features of WebApps compared to traditional software applications. A review of the ISO software quality models follows in Section 3; we also discuss what is missing in these models for the Web features. Section 4 illustrates the proposed extension to ISO quality models in order to specify the quality of information. Then, we analyze our proposal in the light of related work, and, finally, we draw concluding remarks.
First, the aim is to introduce the main features of the Web 2.0 highlighting some of its applications; second, to outline the distinctive features of WebApps compared to traditional software applications.
The first WebApps can be grouped in the Web 1.0 era,
and they can be categorized into static and dynamic; most
recent WebApps can be grouped in the so-called Web 2.0
era as per O’Reilly [
WebApps like blogs are significant examples. • Sharing information: in social network people share interests and activities. Examples of these applications are ‘myspace.com’, ‘facebook.com’ and ‘orkut.com’. • Endless beta condition: considering the above three features it is easy to understand that Web 2.0 apps are mostly dynamic and under ongoing changes. Wikipedia is for instance continually subject to editing by users so there is no a ‘final version’ of it.
In addition, Murugesan [
Aesthetic and visual features of Web development are not just a technical skill but also an artistic skill. • Internationalization and accessibility of contents for users with various disabilities are real and challenging issues in WebApps, independently of eras. • Searching and browsing are two basic functionalities used to find and explore information and services. • Security is a central issue in data-transaction-oriented WebApps. Likewise, performance is also critical for many WebApps, although both are also critical features for traditional applications. • The medium where WebApps are hosted and delivered is generally more unpredictable than the medium where traditional software applications run. For instance, unpredictability in bandwidth maintenance, or in server availability, can affect the perceived quality that users could have. • Contents privacy and intellectual property rights of materials are current issues too. They involve ethic, cultural, and legal aspects as well.
Most of the above features make a WebApp a particular artifact. However, like any software application, it also involves source and executable code, persistent structured data, architectural design and so on. Ultimately, many of the above features will influence the way quality requirements are modeled. We need to deal not only with usability, functionality, efficiency, reliability and maintainability, as in traditional software products but also with info quality, i.e. with content accuracy, suitability, accessibility, and legal compliance.
The concept of quality is not simple and atomic, but
a multidimensional and relative one. Common practice
assesses quality by means of the quantification of lower
abstraction concepts, such as attributes of entities. The
attribute can be briefly defined as a measurable property
of an entity category. Therefore, quality – and its
subdimensions, called characteristics and sub-characteristics
in the ISO 9126-1 standard – is an abstract relationship
between attributes of an entity and a specific information
need, with regard to its purpose, context, and user’s
viewpoint [
The ISO 9126-1 standard (and the ongoing SQuaRE
project) distinguishes among three different approaches to
software product quality, viz. internal quality, external
quality, and quality in use. These three views of quality in
ISO 9126-1 can be summarized as follows [
The same quality model have been maintained both to internal and external views (see Fig. 1). For instance, functionality characteristic is defined as “the capability of the software product to provide functions which meet stated and implied needs when the software is used under specified conditions”. It has in turn five subcharacteristics, i.e. accuracy, suitability, security, interoperability and compliance. Functionality – from the nonfunctional requirement point of view – is concerned with what the software does to fulfill the user needs (software is defined as a set of programs with the associated data and documentation). Considering for example the accuracy and security definitions both function and data attributes can be associated in order to assess them. This is also valid for WebApps where programs and persistent, structured data (and its effects) are there as well. Note that in the information quality literature data and information quality are treated very often as synonymous terms but we make a clear difference as we discuss later on.
Besides, usability characteristic is defined as “the capability of the software product to be understood, learned, used and attractive to the user, when used under specified conditions”. Usability is subdivided in turn into five sub-characteristics, i.e. understandability, learnability, operability, attractiveness, and compliance. Usability and its sub-characteristics apply also to specifying internal and external quality requirements for WebApps.
Lastly, the core aim in designing a WebApp is to provide users with degrees of excellence or quality in use by interacting with the application and by performing its tasks comfortably. Regarding the spirit of the ISO 9126-1 standard, quality in use is the end user’s view of the quality of a running system containing software, and is measured and evaluated in terms of the result of using it rather than by properties of the software itself. Ultimately, taking into account meaningful software or WebApp attributes for internal quality are a prerequisite to achieve the required external behavior, and considering meaningful software attributes to external behavior are a prerequisite to achieve quality in use. 3.2 ISO
Consequently, we argue that the software quality
models introduced above are also applicable to a great
extent to intermediate and final lifecycle Web products.
Note this discussion is an extension of that made in [
Like any software production line, the Web lifecycle involves different stages of its products, whether in early phases as inception and development, or in late phases as deployment, operation, and evolution. To assure the quality of products, we can plan to do it by evaluating and controlling the quality from intermediate products to final products. Thus, to the general question, if we can apply to WebApps the same ISO internal and external quality, and quality in use models, the natural answer is yes.
Nevertheless, to the more specific question whether we can use the same six prescribed quality characteristics (and their sub-characteristics) for internal and external quality requirements, and the four characteristics for quality in use requirements, our answer is yes for the latter, but some other considerations might be taken into account for the former. As highlighted in Section 2, the very nature of WebApps is a mixture of content, functions and services. Therefore we argue that the set of six characteristics, i.e. functionality, usability, reliability, efficiency, maintainability and portability, and their subcharacteristics respectively, are not well suited (or they were not intended) to specify requirements for information quality.
At this point, we would like to introduce the slight difference in meaning between data and information terms. A piece of data is raw material; even though it has some degree of information. Data come from attribute measurements, facts, formula calculations, etc. and basically they have categorical or numerical values, a scale type, and may also have an explicit procedure to produce or collect them. Structured data sets are often represented in databases. On the other hand, information has an added value over data. That is, information is the meaningful interpretation of data for a given context, purpose, and user viewpoint. Usually, in a traditional software program there are functions and data. Very often a webpage is content oriented, i.e. is intended to deliver information (usually unstructured semantically). For example, this article could be hyperlinked and posted as content Web pages. Also a webpage component, e.g. a shopping cart, can edit an item quantity and recalculate prices (a function over data).
Therefore, the central issue is how we can specify and model the content quality for WebApps from the internal and external quality viewpoints. Not only need we deal with usability, functionality, efficiency, reliability, and maintainability but also with the content quality characteristic, which in turn can be subdivided into content accuracy, suitability, accessibility, and legal compliance sub-characteristics, as shown in Fig. 1.
As a consequence, we propose to include the content characteristic and its sub-characteristics in the internal and external quality model of the ISO standard. A point worth mentioning is that in the spirit of the ISO 9126-1 standard is stated “evaluating product quality in practice requires characteristics beyond the set at hand”.
On the other hand, the quality in use definition may be
rephrased as “the capability of the software or WebApp
product to enable specified users to achieve specified
goals with effectiveness, productivity, safety and
satisfaction in specified context of use”. Note that
effectiveness, productivity, safety, and satisfaction are
influenced not only by the usability, functionality,
reliability, efficiency, and content of a WebApp, but also
by two resource components of the context of use. The
context of use depends on both the infrastructure (i.e. the
computer, network, or even the physical working medium)
and the user-oriented goals, i.e. the supported WebApp
tasks and the properties of the user type such as level of IT
training, expertise, age, and cultural issues as well. (See
for example the quality in use case study for an e-learning
WebApp [
Next, we present the proposed ISO internal and external requirement extension in order to include the content characteristic for WebApps independently of Web eras. However, specific attributes associated to content sub-characteristics may be considered for Web 2.0 applications.
As aforementioned information has added value over
data, and hereafter we consider Web information as Web
content, which can be textual or other media. Hence, we
define content as “the capability of a Web product to
deliver information which meets stated and implied needs
when used under specified conditions”. Taking into
account previous contributions made in the area of
information quality – as we will discuss in the related
work section – we have primarily identified four major
sub-characteristics for the content characteristic, which
can help to measure and evaluate information quality
requirements for WebApps. This initial proposal was
made in [
The content sub-characteristics are: First, the content
accuracy, which addresses the very intrinsic nature of the
information quality; second, content suitability, which
addresses the contextual nature of the information quality;
it emphasizes the importance of conveying the appropriate
information for user-oriented tasks and goals; in other
words, it highlights the quality requirement that content
must be considered within the context of use and the
intended audience; third, content accessibility, which
emphasizes the importance of technical and
representational aspects in order to make Web contents
more accessible for users with various disabilities as
regarded in [
Definition The capability of a Web product to deliver information that is correct, credible and current.
The capability of a Web product to deliver information with the right coverage, added value, and consistency, considering the specified user tasks and goals.
The capability of a Web product to deliver information that is accessible for all users (with or without disabilities) taking into account both technical and representational aspects.
The capability of the Web product to adhere to standards, conventions, and legal norms related to content as well as to intellectual property rights.
In addition to the above content sub-characteristics, others to information architecture and organization could be addressed. Many of these sub-characteristics, such as global understandability, learnability, and also operability and attractiveness, can be related to the usability characteristic. Besides, other particular features of WebApps such as search and navigation functionalities can be specified in the functionality sub-characteristics; for example, are the basic and advanced search suitable for the end user? Or, are they tolerant of misspelled words and accurate in retrieving documents? In the same way, we can represent link and page maturity attributes, or attributes to deficiencies due to browsers’ compatibility into the reliability sub-characteristics.
On the other hand, from the quality in use perspective, we have proposed to use the same ISO model (recall subsection 3.2). As a matter of fact, for the satisfaction characteristic, specific (questionnaire) items for evaluating quality of content should be included.
Finally, we have performed some preliminary studies.
One of them was a quantitative evaluation for a shopping
cart of a Web 1.0 app, where the content accuracy and
suitability sub-characteristics have intervened [
Recently, a qualitative evaluation was made [
First of all, it should be highlighted that the process of content production in Web 1.0 apps pursues rather a topdown approach, i.e., only content providers supply information to users. Conversely, in Web 2.0 apps this process becomes rather bottom-up; that is, mainly final users upload and update information. Moreover, content is submitted to a social control mechanism since users can share, edit, or comment content of other users, e.g. blog, wiki, social network. In fact, initial observations have shown that some kind of information may be considered more accurate and suitable in ‘tripadvisor.com’ than in ‘opodo.co.uk’; particularly, information referring for instance to hotel review, location comment. In contrast, information as flight timetables, holiday price lists, etc. can be considered more accurate and suitable in ‘opodo.co.uk’. Lastly, in general terms we argue that the WebApp’s content quality does not depend on the kind of applications – whether Web 1.0 or Web 2.0; however, some kind of contents and services are more appropriate for Web 1.0 apps, while others for Web 2.0.
Ultimately, we can state the content sub-characteristics we have specified for evaluation purposes can be applied to all WebApps, independently from which era they belong.
The model presented in this paper, as an extension of
the ISO 9126-1 quality models, has been elaborated taken
also into account related researches about dimensions of
data and information quality. We next remark the main
information quality models, often called frameworks in the
literature, developed over the last years. The reader can,
however, find broader reviews for WebApps for instance
in [
It is worth mentioning that the difference in meaning between data and information – as remarked in subsection 3.2 – has often been neglected in these quality frameworks. Moreover, very often – and in some cases explicitly – these terms are used interchangeably.
Content Accuracy 1.1. Correctness, the extent to which information is reliable in the sense of being free of errors. 1.2. Believability (synonym: Credibility), the extent to which the information is reputable, objective, and verifiable. 1.2.1. Authority (synonym: Reputability), the extent to which the source of the information is trustworthy. 1.2.2. Objectivity, the extent to which the content (i.e., information or facts) is unbiased and impartial. 1.2.3. Verifiability (synonym: Traceability), the extent to which the owner and/or author of the content can be verified. 1.3. Currency (synonym: Up-to-dateness), the extent to which the information can be identified as up to date. Content Suitability 2.1. Value-added, the extent to which the content can be novel, beneficial, and contribute to react to a given user for the task at hand. 2.1.1. Novelty (synonym: Freshness), the extent to which the information is fresh and contributes to make new decisions for an intended user goal. 2.1.2. Beneficialness, the extent to which the information is advantageous and contributes to make new decisions for an intended user goal.
2.1.3. Reactiveness, the extent to which the information is compelling and contributes to react for an intended user goal. 2.2. Coverage, the extent to which the content is appropriate, complete but also concise for the task at hand to a given user. 2.2.1. Appropriateness, the extent to which the information coverage fits to an intended user goal. 2.2.2. Completeness, the extent to which the information coverage is the sufficient amount of information to an intended user goal.
2.2.3. Conciseness, the extent to which the information coverage is compactly represented without being overwhelming. 2.3. Consistency, the extent to which the content is consistent to the site’s piece of information or page with respect to the
One of the first studies intended to categorize data
quality dimensions was made by Strong et al [
They developed a framework made up by four categories – intrinsic, contextual, representational, and accessibility – including 16 dimensions of data quality.
Specifically, the intrinsic category indicates that
information has its own quality per se. It contains four
dimensions: accuracy, objectivity, believability, and
reputation. The accessibility category states that
information must be easily accessible but secure. It
includes: accessibility, and security dimensions. The third
category is contextual data quality, which indicates that
information should be provided in time and in appropriate
amounts. It includes: relevancy, value-added, timeliness,
completeness, and amount of data. The last category is
representational data quality, which focuses on format of
data/information and its meaning. It includes:
interpretability, ease of understanding, concise
representation, and consistent representation. As a matter
of fact, this quality framework was initially developed for
traditional information systems. Nevertheless, this model
has been used for WebApps too. For instance,
Katerattanakul et al [
A different slightly way to model and evaluate the
quality of information for a WebApp – both at page and
site level – is proposed by Alexander et al [
The first published study about extending the ISO 9126
model has been made by Zeist et al [
According to Vaníček [
Most WebApps, besides the increasing support to functionalities and services will continue aiming at showing and delivering content. This basic feature stemming from the early Web 1.0 applications is currently empowered by the Web 2.0 and follow-on applications. Web 2.0 applications rely strongly on actual users sharing, collaborating and performing content tasks in real contexts of use. So evaluating the quality of WebApps is still a challenge.
In the present work, we have proposed how to specify quality requirements for functionalities, services and content for WebApps employing an integrated approach. By reusing and extending the ISO 9126-1 quality models’ characteristics, we have discussed the need of modeling and adding the content characteristic for evaluating the quality of information. Specifically, we have argued that the internal and external quality models with the set of six characteristics, i.e. functionality, usability, reliability, efficiency, maintainability and portability, and their subcharacteristics respectively, are not sufficient to specify WebApps’ information quality requirements. As a consequence, we have proposed to include in both models the content characteristic and its subcharacteristics. Besides, from the quality in use perspective, we have proposed to use the same ISO model. Ultimately, we have tried to give a minimalist and systematic solution to the current concern which is how to identify and model WebApps’ quality and quality in use requirements at different lifecycle stages.