Vol.4 No.1 March 3, 2005
Web Applications
Editorial  (pp001-002)
        N. Koch, P. Fraternali and M. Wirsing       
Research articles:
A Comparison of Two Approaches for Automatic Construction of Web Applications  (pp003-020)
        M. Taguchi, K. Jamroendararasame, K. Asami and T. Tokuda
To support development of consistent and secure Web applications, we have designed a number of Web application generators. These generators can be roughly classified into two types of approaches: an annotation approach and a diagram approach. In this paper, we try to make clear the roles of these generators, and compare the two approaches in terms of target applications, development processes and target users. While both approaches are sufficiently powerful and flexible enough to efficiently construct typical Web applications, the most appropriate generator should be chosen according to the characteristics of the application and the development process.

Adding Client-Side Adaptation to the Conceptual Design of e-Learning Web Applications  (pp021-037)
        S. Ceri, P. Dolog, M. Matera and W. Nejdl
In this paper, we integrate WebML, a high-level model and technology for building server-side Web applications, with UML-Guide, a UML-based system that generates client-side guides for the adaptation of Web applications. The combination of the two systems is shown at work on an e-Learning scenario: WebML is the basis of the specification of a generic e-Learning system, collecting a large number of learning objects, while UML-Guide is used for building company-specific e-Learning curricula. The resulting system can be considered an ``adaptive hypermedia generator'' in full strength, whose potential expressive power goes beyond the experiments reported in this paper.

Fundamentals of Exception Handling within Workflow-Based Web Applications  (pp038-056)
        M. Brambilla and C. Tziviskou
As the Web becomes a platform for implementing B2B applications, the need arises of extending Web conceptual modeling from data-centric applications to data- and process-centric applications. New primitives must be put in place to implement workflows describing business processes. In this context, new problems about process safety arise, due to the loose control on Web clients. Indeed, user behavior can generate dangerous incoherencies for the execution of processes. This paper presents a proposal of workflow-enabling primitives for Web applications, and a high level approach to the management of exceptions that occurs during execution of processes. We present a classification of exceptions that can occur inside workflow-based Web applications, and recovery policies to retrieve coherent status and data after an exception. An implementation experience is briefly presented too.

Interplay of Content and Context  (pp057-078)
        R. Belotti, C. Decurtins, M. Grossniklaus, M.C. Norrie and A. Palinginis
We examine the relationship between context engines and content management systems, showing by means of an example application how these should mutually interact with each other to ensure the timely delivery of relevant information. We show how a content management system can use context information to enrich its functionality and also how a general and abstract approach to content management can support context awareness. Information models of the general context engine and content management system that we have developed are presented, along with a description of how a symbiotic relationship of content and context can be achieved through the integration of these models.

Accelerating Dynamic Web Content Delivery Using Keyword-based Fragment Detection  (pp079-100)
        D. Brodie, A. Gupta and W-S Shi
Recent advances in Web engineering have enabled rapid growth of dynamic Web services such as Web-based email, online banking, online shopping and entertainment. We envision that finding an effective way to deliver these dynamic Web services and understanding the relationship between Web application design and delivery are two important Web engineering issues, and have not been seriously considered in the community. In this paper, we intend to tackle the first problem and pave the way for solving the second problem in the future. To efficiently serve this trend, several server- side and cache-side fragment-based techniques, which exploit reuse of Web pages at the sub-document level, have been proposed. Most of these techniques do not focus on the creation of the fragmented content from existing dynamic content. Also, existing caching techniques do not support fragment movement across the document, a common behavior in dynamic content.}{This paper presents two proposals that we have suggested to solve these problems. The first, DyCA, a dynamic content adapter, takes original dynamic Web content and converts it to fragment-enabled content. Thus the dynamic parts of the document are separated into separate fragments from the static template of the document. This is dependent on our proposed keyword-based fragment detection approach that uses predefined keywords to find these fragments and to split them out of the core document. Our second proposal, an augmentation to the ESI standard, allows splitting the information of the position of each fragment in the template from the template data itself by using a mapping table. Using this, a fragment enabled cache can have a more fine grained level of identifying fragments independent of their location on the template, which enables it to take into account fragment behaviors such as fragment movement.We used the content taken from three real Web sites to achieve a detailed performance evaluation of our proposals. Our results show that our keyword-based approach for fragment detection and extraction provides us with cacheable fragments that, when combined with our proposed mapping table augmentation, can provide significant advantages for fragment-based Web caching of existing dynamic content.

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