Vol.9 No.2 June 1, 2010

Comparison of Common XML-Based Web User Interface Languages (pp095-115)
        Mikko Pohja
In addition to being a platform for information access, the World Wide Web is increasingly becoming an application platform. While web applications have several benefits compared to desktop applications, there are also some problems. With legacy HTML, for example, one cannot produce user interfaces such as those that users have become accustomed to with desktop applications. What worked for static documents is not sufficient for the complicated web applications of today. Several parties have addressed this problem by defining a specific UI description language. In addition, the renewal of HTML aims to enhance support for web applications. This study evaluated five XML-based UI description formats, including HTML 5, in order to determine which language is best suited for modern web application development. The study also assessed what kind of applications are suited to each format. The requirements for a Web UI description language from the literature were revised and three use cases were defined, through which the languages are evaluated. The paper also presents the model differences of the languages.

Schema-based Cache Validation to Improve Query Performance of Web Services (pp116-131)
        A. Raghunathan and K. Murugesan
Web services play a crucial role in e-business, providing application integration within and across enterprises and platforms. Hence there is an increasing need to make web services more efficient and perform better.  Caching of data is a vital factor in improving the QoS and query performance of web-based applications. Invalidation mechanisms are used to refresh cache when accessing dynamic data from backend data sources.  Time or expiry-based cache validation is suitable for enterprise applications where the data does not change very frequently. However, existing expiry-based caching solutions act at the URL/query level, thus increasing access to the data source and hence the response time. In this paper, we propose a time-based caching technique based on the schema of the data source. Our method performs cache validation at the levels of tables and columns, thus minimizing database access. Moreover, the column level granularity avoids database visits for queries that do not access expired columns. We have used simulations to test our design and the results show a significant improvement in reduction of database accesses for web applications thereby reducing bandwidth usage, server load and network traffic.

Incorporating Usability Requirements In a Test/Model-Driven Web Engineering Approach (pp132-156)
        Esteban Robles Luna, Jose I. Panach, Julián Grigera, Gustavo Rossi, and Oscar Pastor
The success of Web applications is constrained by two key features: fast evolution and usability. Current Web engineering approaches follow a "unified" development style which tends to be unsuitable for applications that need to evolve fast. Moreover, according to the quality standard ISO 9126-1, usability is a key factor to obtain quality systems. In this paper, we show how to address usability requirements in a test-driven and model-based Web engineering approach. More specifically, we focus on usability requirements with functional implications, which do not only concern the visual appearance, but also the architecture design. Usability requirements are contemplated from the very beginning of each cycle, by creating a set of meaningful tests that drive the development of the application and ensure that no functionality related to usability is altered unintentionally through development cycles. Dealing with those usability requirements in the very early steps of the software development process avoids future hard changes in the system architecture to support them. The approach is illustrated with an example in the context of the OOWS suite.

Engineering Concern-Sensitive Navigation Structures, Concepts, Tools and Examples (pp157-185)
        Sergio Firmenich, Gustavo Rossi, Matias Urbieta, Silvia Gordillo, Cecilia Challiol, Jocelyne Nanard, Marc Nanard, and Joao Araujo
Improving navigability in Web applications is a serious challenge for developers as this quality feature is essential for applications success. In this paper we present the concept of concern-sensitive navigation, a useful conceptual tool to improve navigation by profiting from the nature of application’s concerns. Concern sensitive navigation allows enriching Web pages with information, services or links related with the context in which pages are accessed. We show how our ideas are applied during the development process (e.g. by applying wise design strategies for separation of concerns) and can also be used by final users while adapting an application (e.g. by modding). Some examples of Web 2.0 sites are used to illustrate this last possibility. We also compare our research with other similar approaches such as the construction of adaptive Web applications.

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