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Astract: Model-Driven Engineering (MDE) places models as firstclass artifacts throughout the software lifecycle requiring the availability of proper transformation languages. Most of today's approaches use declarative rules to specify a mapping between source and target models which is then executed by a transformation engine. Transformation engines, however, most often hide the operational semantics of the mapping and operate on a considerable lower level of abstraction, thus hampering debugging. To tackle these limitations we propose a framework called TROPIC (Transformations on Petri Nets in Color) providing a DSL on top of Colored Petri Nets (CPNs) to specify, simulate, and formally verify model transformations. The formal underpinnings of CPNs enables simulation and veri fication of model transformations. By exploring the constructed state space of CPNs we show how prede fined behavioral properties as well as custom state space functions can be applied for observing and tracking origins of errors during debugging.

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Astract: In the Model-Driven Architecture (MDA) paradigm the Query/View/Transformation (QVT) standard plays a vital role for model transformations. Especially the high-level declarative QVT Relations language, however, has not yet gained widespread use in practice. This is not least due to missing tool support in general and inadequate debugging support in particular. Transformation engines interpreting QVT Relations operate on a low level of abstraction, hide the operational semantics of a transformation and scatter metamodels, models, QVT code, and trace information across different artifacts. We therefore propose a model-based debugger representing QVT Relations on bases of TROPIC, a model transformation language utilizing a variant of Colored Petri Nets (CPNs). As a prerequisite for convenient debugging, TROPIC provides a homogeneous view on all artifacts of a transformation on basis of a single formalism. Besides that, this formalism also provides a runtime model, thus making the afore hidden operational semantics of the transformation explicit. Using an explicit runtime model allows to employ model-based techniques for debugging, e.g., using the Object Constraint Language (OCL) for simply defining breakpoints and querying the execution state of a transformation.

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Astract: Ubiquitous web applications (UWA) are a new type of web applications which are accessed in various contexts, i.e. through different devices, by users with various interests, at anytime from anyplace around the globe. For such full-fledged, complex software systems, a methodologically sound engineering approach in terms of model-driven engineering (MDE) is crucial. Several modeling approaches have already been proposed that capture the ubiquitous nature of web applications, each of them having different origins, pursuing different goals and providing a pantheon of concepts. This paper aims to give an in-depth comparison of seven modeling approaches supporting the development of UWAs. This methodology is conducted by applying a detailed set of evaluation criteria and by demonstrating its applicability on basis of an exemplary tourism web application. In particular, five commonly found ubiquitous scenarios are investigated, thus providing initial insight into the modeling concepts of each approach as well as to facilitate their comparability. The results gained indicate that many modeling approaches lack a proper MDE foundation in terms of meta-models and tool support. The proposed modeling mechanisms for ubiquity are often limited, since they neither cover all relevant context factors in an explicit, self-contained, and extensible way, nor allow for a wide spectrum of extensible adaptation operations. The provided modeling concepts frequently do not allow dealing with all different parts of a web application in terms of its content, hypertext, and presentation levels as well as their structural and behavioral features. Finally, current modeling approaches do not reflect the crosscutting nature of ubiquity but rather intermingle context and adaptation issues with the core parts of a web application, thus hampering maintainability and extensibility. Different from other surveys in the area of modeling web applications, this paper specifically considers modeling concepts for their ubiquitous nature, together with an investigation of available support for MDD in a comprehensive way, using a well-defined as well as fine-grained catalogue of more than 30 evaluation criteria.

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Astract: Today's online model repositories offer to download and view the textual specifications of e.g. metamodels and models in the browser. For users, in order to efficiently search a model repository, a graphical visualization of the stored models is desirable. First attempts that automatically generate class diagrams as bitmaps, however, do not scale for large models and fail to present all information. In this paper, we present our Web 2.0 MetaModelbrowser, a model visualization service which provides an Ajax-based tree-viewer for efficiently browsing Ecore-based metamodels and their models. As a main contribution of this work the MetaModelbrowser is complementary to existing model repositories in that its visualization service can be integrated into them. The MetaModelbrowser, furthermore, allows zooming in and out of the details of arbitrarily sized models as necessary. Furthermore, we have done some case studies on the one hand how to extend the MetaModelbrowser, e.g., for creation, update, and deletion of model elements as well as supporting model weaving, and on the other hand how to incorporate the MetaModelbrowser in current versioning systems.

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Astract: Seamless exchange of models among different modeling tools increasingly becomes a crucial prerequisite for the success of modeldriven engineering. Current best practices use model transformation languages to realize necessary mappings between concepts of the metamodels defining the modeling languages supported by different tools. Existing model transformation languages, however, lack appropriate abstraction mechanisms for resolving recurring kinds of structural heterogeneities one has to primarily cope with when creating such mappings. We propose a framework for building reusable mapping operators which allow the automatic transformation of models. For each mapping operator, the operational semantics is specified on basis of Colored Petri Nets, providing a uniform formalism not only for representing the transformation logic together with the metamodels and the models themselves, but also for executing the transformations, thus facilitating understanding and debugging. To demonstrate the applicability of our approach, we apply the proposed framework for defining a set of mapping operators which are intended to resolve typical structural heterogeneities occurring between the core concepts usually used to define metamodels.