Tanja Mayerhofer

xMOF: Executable DSMLs Based on fUML

The basic ingredients of a domain-specific modeling language (DSML) are its syntax and semantics. For defining the abstract syntax in terms of metamodels, MOF constitutes a standardized language. For specifying the behavioral semantics, however, no standardized language exists, which hampers the emergence of model execution facilities, such as debugging and simulation support. The contribution of this paper is an integrated approach for specifying the abstract syntax and behavioral semantics of DSMLs based exclusively on standardized modeling languages. In particular, we integrate fUML, a standardized executable subset of UML, with MOF leading to a new metamodeling language xMOF. Moreover, we propose a methodology for developing executable DSMLs fostering the separation of abstract syntax and behavioral semantics. To evaluate our approach, we provide an EMF-based implementation and report on lessons learned from performing three case studies in which we implemented executable DSMLs using xMOF.

A runtime model for fUML

With the introduction of fUML, an OMG standard defining the operational semantics of a subset of UML and the conforming virtual machine, UML models can be used not only for informal design sketching but also for completely building executable systems. Although this has been an important step for UML, the full potential of having executable UML models, such as enabling runtime analysis and adaptation, cannot be realized using the standardized virtual machine due to the lack of the adequate means for accessing important runtime information and controlling the execution of UML models. In this paper, we aim at establishing the necessary basis to overcome this limitation. Therefore, we introduce extensions of the standardized fUML virtual machine in terms of a dedicated trace model, an event model, and a command API. We provide an open-source implementation of the proposed extensions, as well as a model debugger for UML models based on this implementation to demonstrate the feasibility of the presented concepts.

Semantic Model Differencing Utilizing Behavioral Semantics Specifications

Identifying differences among models is a crucial prerequisite for several development and change management tasks in model-driven engineering. The majority of existing model differencing approaches focus on revealing syntactic differences which can only approximate semantic differences among models. Significant advances in semantic model differencing have been recently made by Maoz et al [16] who propose semantic diff operators for UML class and activity diagrams. In this paper, we present a generic semantic differencing approach which can be instantiated to realize semantic diff operators for specific modeling languages. Our approach utilizes the behavioral semantics specification of the considered modeling language, which enables to execute models and capture execution traces representing the models’ semantic interpretation. Based on this semantic interpretation, semantic differences can be revealed.

Execution framework of the GEMOC studio (tool demo)

The development and evolution of an advanced modeling environment for a Domain-Specific Modeling Language (DSML) is a tedious task, which becomes recurrent with the increasing number of DSMLs involved in the development and management of complex software-intensive systems. Recent efforts in language workbenches result in advanced frameworks that automatically provide syntactic tooling such as advanced editors. However, defining the execution semantics of languages and their tooling remains mostly hand crafted. Similarly to editors that share code completion or syntax highlighting, the development of advanced debuggers, animators, and others execution analysis tools shares common facilities, which should be reused among various DSMLs. In this tool demonstration paper, we present the execution framework offered by the GEMOC studio, an Eclipse-based language and modeling workbench. The framework provides a generic interface to plug in different execution engines associated to their specific metalanguages used to define the discrete-event operational semantics of DSMLs. It also integrates generic runtime services that are shared among the approaches used to implement the execution semantics, such as graphical animation or omniscient debugging.

Testing and debugging UML models based on fUML

Model-driven development, which has recently gained momentum in academia as well as in industry, changed the software engineering process significantly from being code-centric to being model-centric. Models are considered as the key artifacts and as a result the success of the whole software development process relies on these models and their quality. Consequently, there is an urgent need for adequate methods to ensure high quality of models. Model execution can serve as the crucial basis for such methods by enabling to automatically test and debug models. Therefore, lessons learned from testing and debugging of code may serve as a valuable source of inspiration. However, the peculiarities of models in comparison to code, such as multiple views and different abstraction levels, impede the direct adoption of existing methods for models. Thus, we claim that the currently available tool support for model testing and debugging is still insufficient because these peculiarities are not adequately addressed. In this work, we aim at tackling these shortcomings by proposing a novel model execution environment based on fUML, which enables to efficiently test and debug UML models.

Model-based co-evolution of production systems and their libraries with AutomationML

System models are essential in planning, designing, realizing, and maintaining production systems. AutomationML (AML) is an emerging standard to represent and exchange heterogeneous artifacts throughout the complete system life cycle and is more and more used as a modeling language. AML is designed as a flexible, prototype-based language able to represent the full spectrum of different artifacts. It may be utilized to build reusable libraries containing prototypical elements to build up production systems by using clones. However, libraries have to evolve over time, e.g., to reflect bug fixes, new features or refactorings, and so system models have to co-evolve to reflect the changes in the libraries. To tackle this co-evolution challenge, we specify in this paper the relationship between library elements, i.e., prototypes, and system elements, i.e., clones, by establishing a formal model for prototype-based modeling languages. Based on this formalization, we introduce several levels of consistency rigor one may want to achieve when modeling with prototype-based languages. These levels are also the main input to reason about the impact of library changes on the concrete system models for which we provide semi-automated co-evolution propagation strategies. We apply the established theory to the concrete AML case and present concrete tool support for evolving AML models based on Eclipse which demonstrates that consistency between system models and libraries may be maintained semi-automatically.

Towards xMOF: executable DSMLs based on fUML

When defining a domain-specific modeling language (DSML), the two key components that have to be specified are its syntax and semantics. For specifying a modeling languages abstract syntax, metamodels are the standard means. MOF provides a standardized, well established, and widely accepted metamodeling language enabling the definition of metamodels and the generation of accompanying modeling facilities. However, no such standard means exist for specifying the behavioral semantics of a DSML. This hampers the efficient development of model execution facilities, such as debugging, simulation, and verification. To overcome this limitation, we propose to integrate fUML with MOF to enable the specification of the behavioral semantics for DSMLs in terms of fUML activities. We discuss alternatives how this integration can be achieved and show by-example how to specify the semantics of a DSML using fUML. To reuse existing runtime infrastructures, we further demonstrate the usage of external libraries in fUML-based specifications.

Cross-disciplinary engineering with AutomationML and SysML

Abstract AutomationML (AML) is an emerging standard in the automation domain to represent and exchange artifacts between heterogeneous engineering tools used in different disciplines, such as mechanical and electrical engineering. The Systems Modeling Language (SysML) is a modeling standard influenced by software modeling languages, such as UML, typically adopted in the early phases of engineering processes. This paper investigates commonalities and differences of the structural modeling parts of AML (CAEX) and SysML (block diagrams) in support of establishing tool-independent interoperability. This support for cross-disciplinary modeling is facilitated by a bridge between AML and SysML built on model-driven interoperability techniques. We demonstrate the interoperability between AML and SysML with a case study concerning a lab-sized production system.

Combining fUML and profiles for non-functional analysis based on model execution traces

For developing software systems it is crucial to consider non-functional properties already in an early development stage to guarantee that the system will satisfy its non-functional requirements. Following the model-based engineering paradigm facilitates an early analysis of non-functional properties of the system being developed based on the elaborated design models. Although UML is widely used in model-based engineering, it is not suitable for model-based analysis directly due to its lack of formal semantics. Thus, current model-based analysis approaches transform UML models into formal languages dedicated for analyses purpose, which may introduce accidental complexity of implementing the required model transformations. The recently introduced fUML standard provides a formal semantics of a subset of UML enabling the execution of UML models. In this paper, we show how fUML can be utilized for analyzing UML models directly without having to transform them. We present a reusable framework for performing model-based analyses leveraging execution traces of UML models and integrating UML profiles heretofore unsupported by fUML. A case study in the performance analysis domain is used to illustrate the benefits of our framework.

A Generative Approach to Define Rich Domain-Specific Trace Metamodels

Executable Domain-Specific Modeling Languages (xDSMLs) open many possibilities for performing early verification and validation (V&V) of systems. Dynamic V&V approaches rely on execution traces, which represent the evolution of models during their execution. In order to construct traces, generic trace metamodels can be used. Yet, regarding trace manipulations, they lack both efficiency because of their sequential structure, and usability because of their gap to the xDSML. Our contribution is a generative approach that defines a rich and domain-specific trace metamodel enabling the construction of execution traces for models conforming to a given xDSML. Efficiency is increased by providing a variety of navigation paths within traces, while usability is improved by narrowing the concepts of the trace metamodel to fit the considered xDSML. We evaluated our approach by generating a trace metamodel for fUML and using it for semantic differencing, which is an important V&V activity in the realm of model evolution. Results show a significant performance improvement and simplification of the semantic differencing rules as compared to the usage of a generic trace metamodel.