Bridging WebML to model-driven engineering: from document type definitions to meta object facility

Meta-models are a prerequisite for model-driven engineering (MDE) in general and consequently for model-driven web engineering in particular. Various web modelling languages, however, are not based on meta-models and standards, like object management group's prominent meta object facility (MOF). Instead they define proprietary languages rather focused on notational aspects. Thus, MDE techniques and tools cannot be deployed for such languages preventing to exploit the full potential of MDE in terms of standardised storage, exchange and transformation of models. The WebML web modelling language is one example that does not yet rely on an explicit meta-model in the sense of MDE. Instead, it is defined in terms of a document type definition (DTD), and implicitly within the accompanying tool. Code generation then has to rely on model-to-code transformations based of extensible stylesheet language transformations (XSLT). We propose a meta-model for WebML to bridge WebML to MDE. To establish such a meta-model, instead of remodelling WebML's meta-model from scratch, a semi-automatic approach is provided that allows generating MOF-based meta-models on the basis of DTDs. The meta-model for WebML accomplishes the following aims: first, it represents an initial step towards a transition to employ MDE techniques within the WebML design methodology. Second, the provision of a MOF-based meta-model ensures interoperability with other MDE tools. Third, it represents an important step towards a common meta-model for Web modelling in future.     

Integrating XML and Relational Database Systems

Relational databases get more and more employed in order to store the content of a web site. At the same time, XML is fast emerging as the dominant standard at the hypertext level of web site management describing pages and links between them. Thus, the integration of XML with relational database systems to enable the storage, retrieval, and update of XML documents is of major importance. Data model heterogeneity and schema heterogeneity, however, make this a challenging task. In this respect, the contribution of this paper is threefold. First, a comparison of concepts available in XML schema specification languages and relational database systems is provided. Second, basic kinds of mappings between XML concepts and relational concepts are presented and reasonable mappings in terms of mapping patterns are determined. Third, design alternatives for integrating XML and relational database systems are examined and X-Ray, a generic approach for integrating XML with relational database systems is proposed. Finally, an in-depth evaluation of related approaches illustrates the current state of the art with respect to the design goals of X-Ray.     

Self-maintaining web pages

Data-intensive web-based information systems usually employ database systems to store the contents forming the basis for web page construction. Generating web pages on the fly, especially in peak times, can lead to severe performance problems. Thus, pre-generation of web pages has been suggested to be ready for prime time, allowing to reliably deliver several hundred pre-generated pages per second. Maintaining the consistency of these web pages with respect to changes within the database in an efficient way, however, represents a major challenge. This paper presents a novel approach for “self-maintaining” web pages that is, different to previous approaches, characterized by a simple (and thus, easy to maintain) database-to-web page mapping and very low page re-generation costs. This is achieved by utilizing fragmentation techniques from distributed databases, by allocating parameterized fragment classes to web page classes (rather than individual fragments to single web pages), and using the Extensible Markup Language (XML) as an intermediate layer between the database and the final web pages.     

Engaging end-user driven recommender systems: personalization through web augmentation

Multimedia Tools and Applications - In the past decades recommender systems have become a powerful tool to improve personalization on the Web. Yet, many popular websites lack such functionality,...