Fabian Büttner

USE: A UML-based specification environment for validating UML and OCL

The Unified Modeling Language (UML) is accepted today as an important standard for developing software. UML tools however provide little support for validating and checking models in early development phases. There is also no substantial support for the Object Constraint Language (OCL). We present an approach for the validation of UML models and OCL constraints based on animation and certification. The USE tool (UML-based Specification Environment) supports analysts, designers and developers in executing UML models and checking OCL constraints and thus enables them to employ model-driven techniques for software production.

Model transformations? transformation models!

Much of the current work on model transformations seems essentially operational and executable in nature. Executable descriptions are necessary from the point of view of implementation. But from a conceptual point of view, transformations can also be viewed as descriptive models by stating only the properties a transformation has to fulfill and by omitting execution details. This contribution discusses the view that model transformations can be abstracted as being transformation models. As a simple example for a transformation model, the well-known transformation from the Entity-Relationship model to the Relational model is shown. A transformation model in this contribution is nothing more than an ordinary, simple model, i.e., a UML/MOF class diagram together with OCL constraints. A transformation model may transport syntax and semantics of the described domain. The contribution thus covers two views on transformations: An operational model transformation view and a descriptive transformation model view.

Verification of ATL transformations using transformation models and model finders

In model-driven engineering, models constitute pivotal elements of the software to be built. If models are specified well, transformations can be employed for different purposes, e.g., to produce final code. However, it is important that models produced by a transformation from valid input models are valid, too, where validity refers to the metamodel constraints, often written in OCL. Transformation models are a way to describe this Hoare-style notion of partial correctness of model transformations using only metamodels and constraints. In this paper, we provide an automatic translation of declarative, rule-based ATL transformations into such transformation models, providing an intuitive and versatile encoding of ATL into OCL that can be used for the analysis of various properties of transformations. We furthermore show how existing model verifiers (satisfiability checkers) for OCL-annotated metamodels can be applied for the verification of the translated ATL transformations, providing evidence for the effectiveness of our approach in practice.

A Benchmark for OCL Engine Accuracy, Determinateness, and Efficiency

The Object Constraint Language (OCL) is a central element in modeling and transformation languages like UML, MOF, and QVT. Consequently approaches for MDE (Model-Driven Engineering) depend on OCL. However, OCL is present not only in these areas influenced by the OMG but also in the Eclipse Modeling Framework (EMF). Thus the quality of OCL and its realization in tools seems to be crucial for the success of model-driven development. Surprisingly, up to now a benchmark for OCL to measure quality properties has not been proposed. This paper puts forward in the first part the concepts of a comprehensive OCL benchmark. Our benchmark covers (A) OCL engine accuracy (e.g., for the undefined value and the use of variables), (B) OCL engine determinateness properties (e.g., for the collection operations any and flatten), and (C) OCL engine efficiency (for data type and user-defined operations). In the second part, this paper empirically evaluates the proposed benchmark concepts by examining a number of OCL tools. The paper discusses several differences in handling particular OCL language features and underspecifications in the OCL standard.

On validation of ATL transformation rules by transformation models

Model-to-model transformations constitute an important ingredient in model-driven engineering. As real world transformations are complex, systematic approaches are required to ensure their correctness. The ATLAS Transformation Language (ATL) is a mature transformation language which has been successfully applied in several areas. However, the executable nature of ATL is a barrier for the validation of transformations. In contrast, transformation models provide an integrated structural description of the source and target metamodels and the transformation between them. While not being executable, transformation models are well-suited for analysis and verification of transformation properties. In this paper, we discuss (a) how ATL transformations can be translated into equivalent transformation models and (b) illustrate how these surrogates can be employed to validate properties of the original transformation.

Lightweight string reasoning for OCL

Models play a key role in assuring software quality in the model-driven approach. Precise models usually require the definition of OCL expressions to specify model constraints that cannot be expressed graphically. Techniques that check the satisfiability of such models and find corresponding instances of them are important in various activities, such as model-based testing and validation. Several tools to check model satisfiability have been developed but to our knowledge, none of them yet supports the analysis of OCL expressions including operations on Strings in general terms. As, in contrast, many industrial models do contain such operations, there is evidently a gap. There has been much research on formal reasoning on strings in general, but so far the results could not be included into model finding approaches. For model finding, string reasoning only contributes a sub-problem, therefore, a string reasoning approach for model finding should not add up front too much computational complexity to the global model finding problem. We present such a lightweight approach based on constraint satisfaction problems and constraint rewriting. Our approach efficiently solves several common kinds of string constraints and it is integrated into the EMFtoCSP model finder.

Realizing UML Metamodel Transformations with AGG

In this paper, we work out equivalence transformations on the UML metamodel as concrete graph transformations implemented in the AGG tool. We consider two examples for manipulating the static structure of a UML model, namely the transformation of an association class into a ternary association and the transformation of a ternary association into three binary associations. We discuss technical details and pros and cons of the presented approach and shortly put out work into the context of the MDA.

Model-driven standardization of public authority data interchange

In the past decade, several electronic data exchange processes between public authorities have been established by the German public administration. In the context of various legacy systems and numerous suppliers of software for public authorities, it is crucial that these interfaces are open and precisely and uniformly defined, in order to foster free competition and interoperability. A community of such projects and specifications for various public administration domains has arisen from an early adopter project in the domain of data interchange between the 5400 German municipal citizen registers. A central coordination office provides a framework for these projects that is put into operation by a unified model-driven method, supported by tools and components, involving UML profiles, model validation, and model-to-text transformations into several technical domains. We report how this model-driven approach has already proven to be effective in a number of projects, and how it could contribute to the development of standardized e-government specifications in various ways. A model-driven method has been successfully applied in e-government standardization.Model validation and model transformation foster time to market and interoperability.The case study reports how the method has been uniformly applied in 8 different projects.

Initiating a Benchmark for UML and OCL Analysis Tools

The Object Constraint Language (OCL) is becoming more and more popular for model-based engineering, in particular for the development of models and model transformations. OCL is supported by a variety of analysis tools having different scopes, aims and technological corner stones. The spectrum ranges from treating issues concerning formal proof techniques to testing approaches, from validation to verification, and from logic programming and rewriting to SAT-based technologies. This paper is a first step towards a well-founded benchmark for assessing validation and verification techniques on UML and OCL models. The paper puts forward a set of UML and OCL models together with particular questions for these models roughly characterized by the notions consistency, independence, consequences, and reachability. The paper sketches how these questions are handled by two OCL tools, USE and EMFtoCSP. The claim of the paper is not to present a complete benchmark right now. The paper is intended to initiate the development of further UML and OCL models and accompanying questions within the UML and OCL community. The OCL community is invited to check the presented UML and OCL models with their approaches and tools and to contribute further models and questions which emphasize the possibilities offered by their own tools.

Checking Model Transformation Refinement

Refinement is a central notion in computer science, meaning that some artefact S can be safely replaced by a refinement R, which preserves S’s properties. Having available techniques and tools to check transformation refinement would enable (a) the reasoning on whether a transformation correctly implements some requirements, (b) whether a transformation implementation can be safely replaced by another one (e.g. when migrating from QVT-R to ATL), and (c) bring techniques from stepwise refinement for the engineering of model transformations.