Elisabeth Kapsammer

Lifting metamodels to ontologies: a step to the semantic integration of modeling languages

The use of different modeling languages in software development makes their integration a must. Most existing integration approaches are metamodel-based with these metamodels representing both an abstract syntax of the corresponding modeling language and also a data structure for storing models. This implementation specific focus, however, does not make explicit certain language concepts, which can complicate integration tasks. Hence, we propose a process which semi-automatically lifts metamodels into ontologies by making implicit concepts in the metamodel explicit in the ontology. Thus, a shift of focus from the implementation of a certain modeling language towards the explicit reification of the concepts covered by this language is made. This allows matching on a solely conceptual level, which helps to achieve better results in terms of mappings that can in turn be a basis for deriving implementation specific transformation code.

X-ray: towards 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. This paper presents X-Ray, a generic approach for integrating XML with relational database systems. The key idea is that mappings may be defined between XML DTDs and relational schemata while preserving their autonomy. This is made possible by introducing a meta schema and meta knowledge for resolving data model heterogeneity and schema heterogeneity. Since the mapping knowledge is not hard-coded but rather reified within the meta schema, maintainability and changeability is enhanced. The meta schema provides the basis for X-Ray to automatically compose XML documents out of the relational database when requested and decompose them when they have to be stored.

Bridging existing Web modeling languages to model-driven engineering: a metamodel for WebML

Metamodels are a prerequisite for model-driven engineering (MDE) in general and consequently for model-driven web engineering in particular. Various modeling languages, just as in the web engineering field, however, are not based on metamodels and standards but instead define proprietary languages rather focused on notational aspects. Thus, MDE techniques and tools can not be deployed for such languages. The WebML web modeling language is one example that does not yet rely on an explicit metamodel. Instead, it is implicitly defined within the accompanying tool in terms of a document type definition (DTD), i.e., a grammar-like textual definition for specifying the structure of XML documents. Code generation then has to rely on XSLT-based model-to-code transformations.In this paper, we propose a metamodel for WebML which is based on the Meta Object Facility (MOF). To establish such a metamodel a semi-automatic approach is provided that allows to generate MOF-based metamodels from DTDs. The metamodel 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, it represents an important step towards a common metamodel for Web modeling. Third, the provision of a MOF-based metamodel ensures interoperability with other MDE tools.

Towards Using UML 2 for Modelling Web Service Collaboration Protocols

In a web environment, graphical specifications of service collaborations which focus on the protocols of collaborating services are especially important, in order to attain the desired properties of interoperability and loose coupling. Different to modelling of generic software component collaborations, additional requirements must be considered, including security and transaction aspects, and the characteristics of specific target technologies such as ebXML and BPEL. This paper describes a UML-based approach for platform independent modelling web service collaboration protocols, which takes into account the specific requirements, and supports mappings to relevant target technologies.

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.

Aspect-Oriented Modeling of Ubiquitous Web Applications: The aspectWebML Approach

Ubiquitous Web applications (UWA) are required to be customizable, meaning their services need to be adaptable towards the context of use, e.g., user, location, time, and device. Considering UWA s from a software engineering point of view, a systematic development on basis of models is crucial. Current Web modeling languages, however, often disregard the crosscutting nature of customization potentially affecting all parts of a Web application, and often mingle core and customization functionality. This leads to inefficient development processes, high maintenance overheads, and a low potential for reuse. We regard customization as a crosscutting concern in the sense of the aspect-oriented paradigm. As a proof of concept, we extend the prominent Web modeling language WebML on basis of our reference architecture for aspect-oriented modeling. This allows for a clear separation between the core and customization functionality, and - as a spin-off - demonstrates how to bridge existing (domain-specific) modeling languages with aspect-oriented concepts

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 groups 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 WebMLs 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.

User profile integration made easy: model-driven extraction and transformation of social network schemas

User profile integration from multiple social networks is indispensable for gaining a comprehensive view on users. Although current social networks provide access to user profile data via dedicated APIs, they fail to provide accurate schema information, which aggravates the integration of user profiles, and not least the adaptation of applications in the face of schema evolution. To alleviate these problems, this paper presents, firstly, a semi-automatic approach to extract schema information from instance data. Secondly, transformations of the derived schemas to different technical spaces are utilized, thereby allowing, amongst other benefits, the application of established integration tools and methods. Finally, as a case study, schemas are derived for Facebook, Google+, and LinkedIn. The resulting schemas are analyzed (i) for completeness and correctness according to the documentation, and (ii) for semantic overlaps and heterogeneities amongst each other, building the basis for future user profile integration.

Consistent co-evolution of models and transformations

Evolving metamodels are in the center of Model-Driven Engineering, necessitating the co-evolution of dependent artifacts like models and transformations. While model co-evolution has been extensively studied, transformation co-evolution has received less attention up to now. Current approaches for transformation co-evolution provide a fixed, restricted set of metamodel (MM) changes, only. Furthermore, composite changes are treated as monolithic units, which may lead to inconsistent co-evolution for overlapping atomic changes and prohibits extensibility. Finally, transformation co-evolution is considered in isolation, possibly inducing inconsistencies between model and transformation co-evolution. To overcome these limitations, we propose a complete set of atomic MM changes being able to describe arbitrary MM evolutions. Reusability and extensibility are supported by means of change composition, ensuring an intra-artifact consistent co-evolution. Furthermore, each change provides resolution actions for both, models and transformations, ensuring an inter-artifact consistent co-evolution. Based on our conceptual approach, a prototypical implementation is presented.

A Survey on Volunteer Management Systems

Voluntary work is indispensable in nearly every area of todays society, e.g., service activities in health care or emergencies. Not least because of this omnipresence of volunteering, already a plethora of volunteer management systems (VMS) has emerged, trying to support diverse volunteering processes and to deal with the broad spectrum and peculiarities of voluntary work. Thus, an in-depth understanding of functional commonalities and differences of VMS is urgently needed. The goal of this paper is therefore to provide an in-depth survey of existing VMS. For this, first, an initial attempt towards a reference model (RM) for VMS is presented, capturing their basic functional ingredients and interrelationships in terms of UML class diagrams. Second, the RM is operationalized by means of a set of evaluation criteria used to compare seven carefully selected VMS, thereby discussing their peculiarities and shortcomings. Third, lessons learned are provided together with research directions for future VMS.