Tihamér Levendovszky

A Systematic Approach to Metamodeling Environments and Model Transformation Systems in VMTS

Highly configurable metamodeling environments and graph transformation techniques have been applied successfully in software system modeling and other areas. In this paper a uniform treatment of these two methods is illustrated by a tool called Visual Modeling and Transformation System. The concepts of an n-layer metamodeling environment is outlined with the related topological and attribute issues. Built on metamodeling techniques two alternatives for model transformation are elaborated, namely, the traversal and the graph-rewriting approaches. In our implementation all of the aforementioned mechanisms use metamodel as a common formalism, which can be considered as a uniform basis for storing, creating and transforming visual languages. The feasibility of the approach is illustrated by a transformation which generates C/C++ code from UML statecharts.

Towards Automated, Formal Verification of Model Transformations

Verification of models and model processing programs are inevitable in real-world model-based software development. Model transformation developers are interested in offline verification methods, when only the definition of the model transformation and the metamodels of the source and target languages are used to analyze the properties and no concrete input models are taken into account. Therefore, the results of the analysis hold for each output model not just particular ones, and we have to perform the analysis only once. Most often, formal verification of model transformations is performed manually or the methods can be applied only for a certain transformation or for the analysis of only a certain property. Previous work has presented a formalism to describe the characteristics of model transformations in separate formal expressions called assertions. This description is based on the first-order logic, therefore, if deduction rules are provided, a reasoning system can use an assertion set to automatically derive additional assertions describing additional properties of model transformations. In this paper, we propose deduction rules and present the verification of a model transformation of processing business process models.

Summary of the workshop on multi-paradigm modeling: concepts and tools

This paper reports on the findings of the first Workshop on Multi-Paradigm Modeling: Concepts and Tools. It contains an overview of the presented papers and of the results of three working groups which addressed multiple views, abstraction, and evolution. Besides this, a definition of the problem space, the main concepts, and an appropriate terminology for multi-paradigm modeling as presented and discussed during the workshop are provided.

Manual and automated performance optimization of model transformation systems

Model-based development is one of the most promising solutions for several problems of industrial software engineering. Graph transformation is a proven method for processing domain-specific models. However, in order to be used by domain experts without graph transformation experts, it must be fast even if not tweaked for speed manually based on knowledge available only to the implementers of the transformation system. In this paper, we compare the performance of such manual optimizations with a solution using automated optimization based on sharing of matches between overlapping left-hand-sides of sequentially independent rules. This yields a 11% improvement in our scenario, although our prototypical implementation only exploits overlapping between, at most, two rules, and the analyzed benchmark does not contain many cases where the optimization is applicable.

Investigating factors influencing the response time in ASP.NET web applications

Distributed systems and network applications play an important role in computer science nowadays. The most common consideration is performance, because these systems have to provide cost-effective and high availability services in the long term, thus they have to be scaled to meet the expected load. The performance of a web application is affected by several factors. The goal of our work is to analyze how some of them affect the response time. The paper presents the result of performance measurements of an ASP.NET web application. We measured the average response time of a test web application while changing the parameters of the application server. The results are analyzed using statistical methods: (i) independence tests to investigate which factors influence principally the performance, (ii) in addition certain plots and hypothesis tests to determine the distribution of the response time.

Metamodel-Based Model Transformation with Aspect-Oriented Constraints

Model transformation means converting an input model available at the beginning of the transformation process to an output model. A widely used approach to model transformation uses graph rewriting as the underlying transformation technique. In case of diagrammatic languages, such as the Unified Modeling Language (UML), the exclusive topological matching is found to be not enough. To define precisely the transformation steps beyond the topology of the visual models, additional constraints must be specified which ensures the correctness of the attributes, or other properties to be enforced. Dealing with OCL constraints provides a solution for these unsolved issues, because topological and attribute transformation methods cannot perform and express the problems which can be addressed by constraint validation. The use of OCL as a constraint and query language in modeling is essential. We have shown that it can be applied to model transformations as well. Often, the same constraint is repetitiously applied in many different places in a transformation. It would be beneficial to describe a common constraint in a modular manner, and to designate the places where it is to be applied. This paper presents the problem of crosscutting constraints in transformation rules, and provides an aspect-oriented solution for it. Our approach makes it possible to define constraints separately from the transformation steps, and facilitates specifying their propagation assignment to graph transformation rules. To illustrate the conceptual results, a case study is also provided, which introduces (i) how our approach generates user interface handler source code for mobile platform from a resource model and a statechart diagram, and (ii) how it validates specific properties during the transformation steps using aspect-oriented constraints.

Performance Factors in ASP.NET Web Applications with Limited Queue Models

Distributed systems and Web applications play an important role in computer science nowadays. The most common consideration is performance, because these systems must provide services with low response time, high availability, and certain throughput level. The performance of a Web application is affected by several factors. The goal of our work is to analyze how some of them affect the response time. In this paper, the effects of two configurable settings of the ASP.NET application server are discussed: the limit of the global queue and the limit of the application queue. The response time of a test Web application are measured, while changing these settings. The results are analyzed in a qualitative manner which is followed by using statistical methods: independence tests to investigate which factors influence principally the performance. Our experiments have shown that the global queue limit and the application queue limit are performance factors. Finally, optimal settings according to the performance-related requirements are determined as a function of client workload and the settings of the thread pool attributes

Validated model transformation-driven software development

Model-driven Software Engineering is one of the most focused research fields. Model processors automatically generate the lower level artefacts. Graph transformation is a widely used technique for model transformations. Especially visual model transformations can be expressed by graph transformations. This paper presents a visual control flow support of the Visual Modelling and Transformation System and discusses the principles of the constraint-driven validated model transformation. The presented approach helps to validate, preserve or guarantee certain model properties not only for individual transformation rules but also for the whole transformation.

Control Flow Support in Metamodel-Based Model Transformation Frameworks

This paper presents the visual control flow support of Visual Modeling and Transformation System (VMTS), which facilitates composing complex model transformations out of simple transformation steps and executing them. The VMTS control flow language (VCFL) uses stereotyped activity diagrams to specify control flow structures and OCL constraints to choose between different control flow branches. In general, a control structure language needs are the sequence, the conditional branch, hierarchism, parallel executions and the iteration. VCFL has all these control structures in a deterministic version

A formalism for describing modeling transformations for verification

Verification of models and model processing programs are inevitable in model-based software development in order to apply them in real-world solutions. Verification of properties of model transformations means to prove that the application of a model transformation generates the expected output models from the input models. Model transformation developers are interested in offline methods for the verification process. Offline analysis means that only the definition of the model transformation and the metmodels of the source and target languages are used to analyze the properties and no concrete input models are taken into account. Therefore, the results of the analysis hold for each output model not just particular ones, and we have to perform the analysis only once. Most often, formal verification of model transformations is performed manually or the methods can be applied only for a certain transformation or for the analysis of only a certain property. In this paper, we propose a formalization to describe model transformation. A formal description can be automatically generated, and can be extended by the experts. An automated reasoning system may prove some properties of model transformations by deriving new assertions from the original description.