Angelika Kusel

Automated verification of model transformations based on visual contracts

Model-Driven Engineering promotes the use of models to conduct the different phases of the software development. In this way, models are transformed between different languages and notations until code is generated for the final application. Hence, the construction of correct Model-to-Model (M2M) transformations becomes a crucial aspect in this approach.Even though many languages and tools have been proposed to build and execute M2M transformations, there is scarce support to specify correctness requirements for such transformations in an implementation-independent way, i.e., irrespective of the actual transformation language used.In this paper we fill this gap by proposing a declarative language for the specification of visual contracts, enabling the verification of transformations defined with any transformation language. The verification is performed by compiling the contracts into QVT to detect disconformities of transformation results with respect to the contracts. As a proof of concept, we also report on a graphical modeling environment for the specification of contracts, and on its use for the verification of transformations in several case studies.

Reuse in model-to-model transformation languages: are we there yet?

In the area of model-driven engineering, model transformations are proposed as the technique to systematically manipulate models. For increasing development productivity as well as quality of model transformations, reuse mechanisms are indispensable. Although numerous mechanisms have been proposed, no systematic comparison exists, making it unclear, which reuse mechanisms may be best employed in a certain situation. Thus, this paper provides an in-depth comparison of reuse mechanisms in model-to-model transformation languages and categorizes them along their intended scope of application. Finally, current barriers and facilitators to model transformation reuse are discussed.

Surviving the heterogeneity jungle with composite mapping operators

Model transformations play a key role in the vision of Model-Driven Engineering. Nevertheless, mechanisms like abstraction, variation and composition for specifying and applying reusable model transformations - like urgently needed for resolving recurring structural heterogeneities - are insufficiently supported so far. Therefore, we propose to specify model transformations by a set of pre-defined mapping operators (MOps), each resolving a certain kind of structural heterogeneity. Firstly, these MOps can be used in the context of arbitrary metamodels since they abstract from concrete metamodel types. Secondly, MOps can be tailored to resolve certain structural heterogeneities by means of black-box reuse. Thirdly, based on a systematic set of kernel MOps resolving basic heterogeneities, composite ones can be built in order to deal with more complex scenarios. Finally, an extensible library of MOps is proposed, allowing for automatically executable mapping specifications since every MOp exhibits a clearly defined operational semantics.

Catch me if you can – debugging support for model transformations

Model-Driven Engineering places models as first-class artifacts throughout the software lifecycle requiring the availability of proper transformation languages. Although numerous approaches are available, they lack convenient facilities for supporting debugging and understanding of the transformation logic. This is because execution engines operate on a low level of abstraction, hide the operational semantics of a transformation, scatter metamodels, models, transformation logic, and trace information across different artifacts, and provide limited verification support. To tackle these problems, we propose a Domain-Specific Language (DSL) on top of Colored Petri Nets (CPNs)—called Transformation Nets—for the execution and debugging of model transformations on a high level of abstraction. This formalism makes the afore hidden operational semantics explicit by providing a runtime model in terms of places, transitions and tokens, integrating all artifacts involved into a homogenous view. Moreover, the formal underpinnings of CPNs enable comprehensive verification of model transformations.

A Petri Net Based Debugging Environment for QVT Relations

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.

Surveying Rule Inheritance in Model-to-Model Transformation Languages

Model transformations play a significant role in Model-Driven Engineering. However, their reuse mechanisms have yet to receive much attention. In this paper, we propose a comparison framework for rule inheritance in model-to-model transformation languages, and provide an in-depth evaluation of prominent representatives of imperative, declarative and hybrid transformation languages. The framework provides criteria for comparison along orthogonal dimensions, covering static aspects, which indicate whether a set of inheriting transformation rules is well-formed at compile-time, and dynamic aspects, which describe how inheriting rules behave at run-time. The application of this framework to dedicated transformation languages shows that, while providing similar syntactical inheritance concepts, they exhibit different dynamic inheritance semantics and offer basic support for checking static inheritance semantics, only.

Towards an expressivity benchmark for mappings based on a systematic classification of heterogeneities

A crucial prerequisite for the success of Model Driven Engineering (MDE) is the seamless exchange of models between different modeling tools demanding for mappings between tool-specific metamodels. Thereby the resolution of heterogeneities between these tool-specific metamodels is a ubiquitous problem representing the key challenge. Nevertheless, there is no comprehensive classification of potential heterogeneities available in the domain of MDE. This hinders the specification of a comprehensive benchmark explicating requirements wrt. expressivity of mapping tools, which provide reusable components for resolving these heterogeneities. Therefore, we propose a feature-based classification of heterogeneities, which accordingly adapts and extends existing classifications. This feature-based classification builds the basis for a mapping benchmark, thereby providing a comprehensive set of requirements concerning expressivity of dedicated mapping tools. In this paper a first set of benchmark examples is presented by means of metamodels and conforming models acting as an evaluation suite for mapping tools.

Reviving QVT Relations: Model-Based Debugging Using Colored Petri Nets

The standardized QVT Relations language, one cornerstone of Model-Driven Architecture (MDA), has not yet gained widespread use in practice, 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 traces across different artifacts. We propose a model-based debugger representing QVT Relations on bases of TROPIC, a model transformation framework which utilizes a variant of Colored Petri Nets (CPNs) providing an explicit runtime model and a homogenous view on all artifacts of a transformation.

Reusing Model Transformations across Heterogeneous Metamodels

Model transformations are key enablers for multi-paradigm modeling. However, currently there is little support for reusing transformations in different contexts since they are tightly coupled to the metamodels they are defined upon, and hence reusing them for other metamodels becomes challenging. Inspired from generic programming, we proposed generic model-to-model transformations, which are defined over so-called metamodel concepts, which are later bound to specific metamodels. Nevertheless, the current binding mechanism lacks automated resolution support for recurring structural heterogeneities between metamodels. Therefore, based on a systematic classification of heterogeneities, we propose a flexible binding mechanism being able to automatically resolve recurring structural heterogeneities between metamodels. For this, the binding model is analyzed and required adaptors are automatically added to the transformation.

Fact or fiction --- reuse in rule-based model-to-model transformation languages

Model transformations are mostly developed from scratch. For increasing development productivity as well as quality of model transformations, reuse mechanisms are indispensable. Although numerous mechanisms have been proposed, no systematic comparison exists making it unclear, which reuse mechanisms may be best employed in a certain situation. Therefore, this paper provides an in-depth comparison of reuse mechanisms in rule-based model-to-model transformation languages and categorizes them along their intended scope of application. For this, a systematic comparison framework for reuse mechanisms is proposed to highlight commonalities as well as differences. Finally, current barriers to model transformation reuse are outlined.