Bridging WebML to Model-Driven Engineering: From DTDs to MOF

Meta-models are a prerequisite for model-driven engineering (MDE) in general and consequently for model-driven web engineering in particular. Various modelling languages, just as in the web engineering field, however, are not based on meta-models and standards, like OMG's prominent Meta Object Facility (MOF). Instead they define proprietary languages rather focused on notational aspects. Thus, MDE techniques and tools can not be deployed for such languages preventing to exploit the full potential of MDE in terms of standardized storage, exchange, and transformation of models. The WebML web modelling language is one prominent 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), i.e., a grammar-like textual definition for specifying the structure of XML documents, and implicitly within the accompanying tool. Code generation then has to rely on XSLT-based model-to-code transformations. In this paper, we propose a meta-model for WebML which is based on the Meta Object Facility (MOF) to bridge WebML to MDE. To establish such a meta-model, instead of re-modelling 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 employing MDE techniques (e.g., model transformations or language extensions through profiles) 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 modeling in the furture.