Least-change bidirectional model transformation with QVT-R and ATL

QVT Relations (QVT-R) is the standard language proposed by the OMG to specify bidirectional model transformations. Unfortunately, in part due to ambiguities and omissions in the original semantics, acceptance and development of effective tool support have been slow. Recently, the checking semantics of QVT-R has been clarified and formalized. In this article, we propose a QVT-R tool that complies to such semantics. Unlike any other existing tool, it also supports meta-models enriched with OCL constraints (thus avoiding returning ill-formed models) and proposes an alternative enforcement semantics that works according to the simple and predictable “principle of least change.” The implementation is based on an embedding of both QVT-R transformations and UML class diagrams (annotated with OCL) in Alloy, a lightweight formal specification language with support for automatic model finding via SAT solving. We also show how this technique can be applied to bidirectionalize ATL, a popular (but unidirectional) model transformation language.     

Colouring: execution,debug and analysis of QVT-relations transformations through coloured Petri nets

QVT is the standard language sponsored by the OMG to specify model-to-model transformations. It includes three different languages, being QVT-relations (QVT-R) the one with higher-level of abstraction. Unfortunately, there is scarce tool support for it nowadays, with incompatibilities and disagreements between the few tools implementing it, and lacking support for the analysis and verification of transformations. Part of this situation is due to the fact that the standard provides only a semi-formal semantics for QVT-R. In order to alleviate this situation, this paper provides a semantics for QVT-R through its compilation into coloured Petri nets. The theory of coloured Petri nets provides useful techniques to analyse transformations (e.g. detecting relation conflicts, or checking whether certain structures are generated or not in the target model) as well as to determine their confluence and termination given a starting model. Our semantics is flexible enough to permit the use of QVT-R specifications not only for transformation and check-only scenarios, but also for model matching and model comparison, not covered in the original standard. As a proof of concept, we report on the use of CPNTools for the execution, debugging, verification and validation of transformations, and on a tool chain (named Colouring) to transform QVT-R specifications and their input models into the input format of CPNTools, as well as to export and visualize the transformation results back as models.     

Case-based exploration of bidirectional transformations in QVT Relations

QVT Relations (QVT-R), a standard issued by the Object Management Group, is a language for the declarative specification of model transformations. This paper focuses on a particularly interesting feature of QVT-R: the declarative specification of bidirectional transformations. Rather than writing two unidirectional transformations separately, a transformation developer may provide a single relational specification which may be executed in both directions. This approach saves specification effort and ensures the consistency of forward and backward transformations. This paper explores QVT-R’s support for bidirectional model transformations through a spectrum of transformation cases. The transformation cases vary with respect to several factors such as the size of the transformation definition or the relationships between the metamodels for source and target models. The cases are solved in QVT-R, but may be applied to other bidirectional transformation languages, as well; thus, they may be used as a benchmark for comparing bidirectional transformation languages. In our work, we focus on the following research questions: functionality of bidirectional transformations in terms of relations between source and target models, solvability (which problems may be solved by a single relational specification of a bidirectional transformation), variability (does a bidirectional transformation contain varying elements, i.e., elements being specific to one direction), comprehensibility (referring to the ease of understanding and constructing QVT-R transformations), and the semantic soundness of bidirectional transformations written in QVT-R.     

Module superimposition: a composition technique for rule-based model transformation languages

As the application of model transformation becomes increasingly commonplace, the focus is shifting from model transformation languages to the model transformations themselves. The properties of model transformations, such as scalability, maintainability and reusability, have become important. Composition of model transformations allows for the creation of smaller, maintainable and reusable transformation definitions that together perform a larger transformation. This paper focuses on composition for two rule-based model transformation languages: the ATLAS Transformation Language (ATL) and the QVT Relations language. We propose a composition technique called module superimposition that allows for extending and overriding rules in transformation modules. We provide executable semantics as well as a concise and scalable implementation of module superimposition based on ATL.     

Formalised EMFTVM bytecode language for sound verification of model transformations

Model-driven engineering is an effective approach for addressing the full life cycle of software development. Model transformation is widely acknowledged as one of its central ingredients. With the increasing complexity of model transformations, it is urgent to develop verification tools that prevent incorrect transformations from generating faulty models. However, the development of sound verification tools is a non-trivial task, due to unimplementable or erroneous execution semantics encoded for the target model transformation language. In this work, we develop a formalisation for the EMFTVM bytecode language by using the Boogie intermediate verification language. It ensures the model transformation language has an implementable execution semantics by reliably prototyping the implementation of the model transformation language. It also ensures the absence of erroneous execution semantics encoded for the target model transformation language by using a translation validation approach.     

扩展QVT Relations实现业务流程模型的转换

QVT(Query/View/Transformation)Relations无法描述包含嵌套模式,因此在描述流程模型的转换规则时存在一些困难.针对此问题,对QVT Relations 进行了扩展,引入了模式因子、嵌套关系表达式和关联端约束这3个概念,并讨论了扩充之后匹配模型和创建模型的语义变化.并用一个例子展示,扩展...     

Comparing relational model transformation technologies: implementing Query/View/Transformation with Triple Graph Grammars

The Model Driven Architecture (MDA) is an approach to develop software based on different models. There are separate models for the business logic and for platform specific details. Moreover, code can be generated automatically from these models. This makes transforma- tions a core technology for MDA and for model-based software engineering approaches in general. Query/View/Transformation (QVT) is the transformation technology recently proposed for this purpose by the OMG. Triple Graph Grammars (TGGs) are another transformation technology proposed in the mid-nineties, used for example in the FUJABA CASE tool. In contrast to many other transformation technologies, both QVT and TGGs declaratively define the relation between two models. With this definition, a transformation engine can execute a transformation in either direction and, based on the same definition, can also propagate changes from one model to the other. In this paper, we compare the concepts of the declarative languages of QVT and TGGs. It turns out that TGGs and declarative QVT have many concepts in common. In fact, QVT-Core can be mapped to TGGs. We show that QVT-Core can be implemented by transforming QVT-Core mappings to TGG rules, which can then be executed by a TGG transformation engine that performs the actual QVT transformation. Furthermore, we discuss an approach for mapping QVT-Relations to TGGs. Based on the semantics of TGGs, we clarify semantic gaps that we identified in the declarative languages of QVT and, furthermore, we show how TGGs can benefit from the concepts of QVT.     

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.     

Semantics of OCL specified with QVT

The Object Constraint Language (OCL) has been for many years formalized both in its syntax and semantics in the language standard. While the official definition of OCL’s syntax is already widely accepted and strictly supported by most OCL tools, there is no such agreement on OCL’s semantics, yet. In this paper, we propose an approach based on metamodeling and model transformations for formalizing the semantics of OCL. Similarly to OCL’s official semantics, our semantics formalizes the semantic domain of OCL, i.e. the possible values to which OCL expressions can evaluate, by a metamodel. Contrary to OCL’s official semantics, the evaluation of OCL expressions is formalized in our approach by model transformations written in QVT. Thanks to the chosen format, our semantics definition for OCL can be automatically transformed into a tool, which evaluates OCL expressions in a given context. Our work on the formalization of OCL’s semantics resulted also in the identification and better understanding of important semantic concepts, on which OCL relies. These insights are of great help when OCL has to be tailored as a constraint language of a given DSL. We show on an example, how the semantics of OCL has to be redefined in order to become a constraint language in a database domain.

基于QVT的模型转换方法研究

针对不同模式之间规则不能重用甚至无法描述嵌套模式的问题．提出一种基于扩展MOF元模型与扩展QVT语言相结合的模型转换方法。该方法通过扩展MOF元模型解决模型之间规则不能重用问题．通过扩展QVTRelations可以增强规则语言的有效性,为模型建立和模型转换提供一种更有效的途径。在一个股票交易系统的转换应用实例中验证该方法的正确性。     

Testing operational transformations in model-driven engineering

Model-driven development is gaining importance in software engineering practice. This increasing usage asks for a new generation of testing tools to verify correctness and suitability of model transformations. This paper presents a novel approach to unit testing QVT operational (QVTO) transformations, which overcomes limitations of currently available tools. Our proposal, called MANTra (Model trANsformation Testing), allows software developers to design test cases directly within the QVTO language and verify them without moving from the transformation environment. MANTra is also available as an eclipse feature that can be easily integrated into established development practice.     

基于四值语义的缺省逻辑

基于公式变换,给出一组缺省理论的变换方法,将命题语言L中的缺省理论变换到对应的命题语言L^-＋中,保证了所得到的缺省理论的所有扩张均不平凡,并通过一种弱变换可同时保证缺省扩张的存在性．为缺省理论定义了各种四值模型,使得缺省逻辑具有非单调超协调推理能力,并证明了L^-＋中的缺省扩张与L中缺省理论的四值模型之间具有一一对应关系．四值模型描述了公式变换的语义,基于四值语义的缺省推理通过缺省理论的变换技术能在标准的缺省逻辑中实现．     

Bridging the gap between formal semantics and implementation of triple graph grammars

The correctness of model transformations is a crucial element for model-driven engineering of high-quality software. A prerequisite to verify model transformations at the level of the model transformation specification is that an unambiguous formal semantics exists and that the implementation of the model transformation language adheres to this semantics. However, for existing relational model transformation approaches, it is usually not really clear under which constraints particular implementations really conform to the formal semantics. In this paper, we will bridge this gap for the formal semantics of triple graph grammars (TGG) and an existing efficient implementation. While the formal semantics assumes backtracking and ignores non-determinism, practical implementations do not support backtracking, require rule sets that ensure determinism, and include further optimizations. Therefore, we capture how the considered TGG implementation realizes the transformation by means of operational rules, define required criteria, and show conformance to the formal semantics if these criteria are fulfilled. We further outline how static and runtime checks can be employed to guarantee these criteria.     

Verification and validation of declarative model-to-model transformations through invariants

In this paper we propose a method to derive OCL invariants from declarative model-to-model transformations in order to enable their verification and analysis. For this purpose we have defined a number of invariant-based verification properties which provide increasing degrees of confidence about transformation correctness, such as whether a rule (or the whole transformation) is satisfiable by some model, executable or total. We also provide some heuristics for generating meaningful scenarios that can be used to semi-automatically validate the transformations.As a proof of concept, the method is instantiated for two prominent model-to-model transformation languages: Triple Graph Grammars and QVT.     

Translating Java for Multiple Model Checkers: The Bandera Back-End

One approach to model checking program source code is to view a model checker as a target machine. In this setting, program source code is translated to a model checker’s input language using a process that shares much in common with program compilation. For example, well-defined intermediate program representations are used to stage the translation through a series of analyses and optimizing transformations and target-specific details are isolated in code generation modules.In this paper, we present the Bandera Intermediate Representation (BIR)—a guarded-assignment transformation system language that has been designed to support the translation of Java programs to a variety of model checkers. BIR includes constructs, such as inheritance, dynamic creation of data, and locking primitives, that are designed to model the semantics of Java primitives. BIR also includes several non-deterministic choice constructs that support abstraction in modeling and specification of properties of dynamic heap structures.We have developed a BIR-based tool infrastructure that has been applied to develop customized analysis frameworks for several different input languages using different model checking tools. We present BIR’s type system and operational semantics in sufficient detail to support similar applications by other researchers. This semantics details several state space reductions and state space search variations. We describe the translation of Java to BIR and how BIR is translated to the input languages of several model checkers.     

An Intuitive Modelling Interface for Systems Biology

We introduce a natural language interface for building stochastic \pi calculus models of biological systems. In this language, complex constructs describing biochemical events are built from basic primitives of association, dissociation and transformation. This language thus allows us to model biochemical systems modularly by describing their dynamics in a narrative-style language, while making amendments, refinements and extensions on the models easy. We give a formal semantics for this language and a translation algorithm into stochastic \pi calculus that delivers this semantics. We demonstrate the language on a model of Fcr receptor phosphorylation during phagocytosis. We provide a tool implementation of the translation into a stochastic \pi calculus language, Microsoft Research''s SPiM, which can be used for simulation and analysis.     

A semantics for Behavior Trees using CSP with specification commands

In this paper we give a formal definition of the requirements translation language Behavior Trees. This language has been used with success in industry to systematically translate large, complex, and often erroneous requirements documents into a structured model of the system. It contains a mixture of state-based manipulations, synchronisation, message passing, and parallel, conditional, and iterative control structures. The formal semantics of a Behavior Tree is given via a translation to a version of Hoare’s process algebra CSP, extended with state-based constructs such as guards and updates, and a message passing facility similar to that used in publish/subscribe protocols. We first provide the extension of CSP and its operational semantics, which preserves the meaning of the original CSP operators, and then the Behavior Tree notation and its translation into the extended version of CSP.     

Comparative Evaluation of Model Transformation Specification Approaches

Model transformations have become a key element of model-driven software development, being used to transform platform-independent models to platform-specific models, to improve model quality, to introduce design patterns and refactorings, and to map models from one language to another. A large number of model transformation notations and tools exist. However, there are no guidelines on how to select appropriate notations for particular model transformation tasks, and no comprehensive comparisons of the relative merits of particular approaches. In this paper we provide a unified semantic treatment of model transformations, and show how correctness properties of model transformations can be defined using this semantics. We evaluate several approaches which have been developed for model transformation specification, with respect to their expressivity, complexity and support for verification, and make recommendations for resolving the outstanding problems concerning model transformation specification.