Invertible Program Restructurings for Continuing Modular Maintenance

When one chooses a main axis of structural decompostion for a software, such as function- or data-oriented decompositions, the other axes become secondary, which can be harmful when one of these secondary axes becomes of main importance. This is called the tyranny of the dominant decomposition. In the context of modular extension, this problem is known as the Expression Problem and has found many solutions, but few solutions have been proposed in a larger context of modular maintenance. We solve the tyranny of the dominant decomposition in maintenance with invertible program transformations. We illustrate this on the typical Expression Problem example. We also report our experiments with Java and Haskell programs and discuss the open problems with our approach.Comment: 6 pages, Early Research Achievements Track; 16th European Conference on Software Maintenance and Reengineering (CSMR 2012), Szeged : Hungary (2012

A heuristic-based approach to code-smell detection

Encapsulation and data hiding are central tenets of the object oriented paradigm. Deciding what data and behaviour to form into a class and where to draw the line between its public and private details can make the difference between a class that is an understandable, flexible and reusable abstraction and one which is not. This decision is a difficult one and may easily result in poor encapsulation which can then have serious implications for a number of system qualities. It is often hard to identify such encapsulation problems within large software systems until they cause a maintenance problem (which is usually too late) and attempting to perform such analysis manually can also be tedious and error prone. Two of the common encapsulation problems that can arise as a consequence of this decomposition process are data classes and god classes. Typically, these two problems occur together – data classes are lacking in functionality that has typically been sucked into an over-complicated and domineering god class. This paper describes the architecture of a tool which automatically detects data and god classes that has been developed as a plug-in for the Eclipse IDE. The technique has been evaluated in a controlled study on two large open source systems which compare the tool results to similar work by Marinescu, who employs a metrics-based approach to detecting such features. The study provides some valuable insights into the strengths and weaknesses of the two approache

On Language Processors and Software Maintenance

This work investigates declarative transformation tools in the context of software maintenance. Besides maintenance of the language specification, evolution of a software language requires the adaptation of the software written in that language as well as the adaptation of the software that transforms software written in the evolving language. This co-evolution is studied to derive automatic adaptations of artefacts from adaptations of the language specification. Furthermore, AOP for Prolog is introduced to improve maintainability of language specifications and derived tools.Die Arbeit unterstützt deklarative Transformationswerkzeuge im Kontext der Softwarewartung. Neben der Wartung der Sprachbeschreibung erfordert die Evolution einer Sprache sowohl die Anpassung der Software, die in dieser Sprache geschrieben ist als auch die Anpassung der Software, die diese Software transformiert. Diese Koevolution wird untersucht, um automatische Anpassungen von Artefakten von Anpassungen der Sprachbeschreibungen abzuleiten. Weiterhin wird AOP für Prolog eingeführt, um die Wartbarkeit von Sprachbeschreibungen und den daraus abgeleiteten Werkzeugen zu erhöhen

High-fidelity metaprogramming with separator syntax trees

Many metaprogramming tasks, such as refactorings, automated bug fixing, or large-scale software renovation, require high-fidelity source code transformations-transformations which preserve comments and layout as much as possible. Abstract syntax trees (ASTs) typically abstract from such details, and hence would require pretty printing, destroying the original program layout. Concrete syntax trees (CSTs) preserve all layout information, but transformation systems or parsers that support CSTs are rare and can be cumbersome to use. In this paper we present separator syntax trees (SSTs), a lightweight syntax tree format, that sits between AST and CSTs, in terms of the amount of information they preserve. SSTs extend ASTs by recording textual layout information separating AST nodes. This information can be used to reconstruct the textual code after parsing, but can largely be ignored when implementing high-fidelity transformations. We have implemented SSTs in Rascal, and show how it enables the concise definition of high-fidelity source code transformations using a simple refactoring for C++

Full Semantics Preservation in Model Transformation – A Comparison of Proof Techniques

Model transformation is a prime technique in modern, model-driven software design. One of the most challenging issues is to show that the semantics of the models is not affected by the transformation. So far, there is hardly any research into this issue, in particular in those cases where the source and target languages are different.\ud \ud In this paper, we are using two different state-of-the-art proof techniques (explicit bisimulation construction versus borrowed contexts) to show bisimilarity preservation of a given model transformation between two simple (self-defined) languages, both of which are equipped with a graph transformation-based operational semantics. The contrast between these proof techniques is interesting because they are based on different model transformation strategies: triple graph grammars versus in situ transformation. We proceed to compare the proofs and discuss scalability to a more realistic setting.\u

Derivation of Change Sequences from State-Based File Differences for Delta-Based Model Consistency

In der sichtenbasierten Software-Entwicklung ist es möglich, dass mehrere Sichten das gleiche Konzept abbilden, wodurch Sichten redundante oder abhängige Informationen darstellen können. Es ist essenziell, diese individuellen Sichten synchron zu halten, um Inkonsistenzen im System zu vermeiden. In Ansätzen mit einem Single Underlying Model (SUM) werden Inkonsistenzen vermieden, indem das SUM als zentrale und einzige Informationsquelle genutzt wird, von welcher Sichten projiziert werden. Um Sichten mit dem SUM zu synchronisieren, wird in den meisten Fällen eine deltabasierte Konsistenzhaltung verwendet. Diese nutzt feingranulare Änderungssequenzen, welche von den einzelnen Sichten bereitgestellt werden müssen, um das SUM inkrementell zu aktualisieren. In realen Anwendungsfällen ist die Funktionalität zur Bereitstellung dieser Änderungssequenzen jedoch selten verfügbar. Stattdessen werden nur zustandsbasierte Änderungen persistiert. Es ist insofern wünschenswert Sichten, welche nur zustandsbasierte Änderungen bereitstellen, in deltabasierter Konsistenzhaltung zu unterstützen. Dies kann erreicht werden, indem die feingranularen Änderungssequenzen von den zustandsbasierten Änderungen abgeleitet werden. In dieser Arbeit wird die Qualität von abgeleiteten Änderungssequenzen im Kontext von Modellkonsistenzhaltung evaluiert. Um eine solche Sequenz abzuleiten, müssen übereinstimmende Elemente aus den verglichenen Modellen identifiziert und deren Unterschiede bestimmt werden. Um übereinstimmenden Elemente zu identifizieren, nutzen wir zwei Strategien. Bei der einen Strategie werden übereinstimmende Elemente anhand ihres eindeutigen Bezeichners erkannt. Bei der anderen Strategie wird eine Ähnlichkeitsmetrik basierend auf den Eigenschaften der Elemente genutzt. Als Evaluationsgrundlage werden verschiedene Testszenarien erstellt. Für jeden Test wird eine initiale und eine geänderte Version von sowohl einem UML-Klassendiagramm als auch Java-Code bereitgestellt. Wir nutzen die verschiedenen Strategien, um Änderungssequenzen basierend auf den zustandsbasierten Änderungen der UML-Sicht abzuleiten, geben diese an das SUM weiter und untersuchen die Ergebnisse in beiden Domänen. Die Ergebnisse zeigen, dass die Strategie, welche eindeutige Bezeichner nutzt, in fast allen betrachteten Fällen (97 %) die korrekte Änderungssequenz liefert. Bei der Nutzung der ähnlichkeitsbasierten Strategie können wir zwei wiederkehrende Fehlermuster identifizieren. Bezüglich dieser Probleme stellen wir eine erweiterte ähnlichkeitsbasierte Strategie vor, welche in der Lage ist, die Auftrittshäufigkeit der Fehlermuster zu reduzieren ohne die Ausführungsgeschwindigkeit signifikant zu beeinflussen

Removal of redundant elements within UML activity diagrams

As the complexity of systems continues to rise, the use of model-driven development approaches becomes more widely applied. Still, many created models are mainly used for documentation. As such, they are not designed to be used in following stages of development, but merely as a means of improved overview and communication. In an effort to use existing UML2 activity diagrams of an industry partner (Daimler AG) as a source for automatic generation of software artifacts, we discovered, that the diagrams often contain multiple instances of the same element. These redundant instances might improve the readability of a diagram. However, they complicate further approaches such as automated model analysis or traceability to other artifacts because mostly redundant instances must be handled as one distinctive element. In this paper, we present an approach to automatically remove redundant ExecutableNodes within activity diagrams as they are used by our industry partner. The removal is implemented by merging the redundant instances to a single element and adding additional elements to maintain the original behavior of the activity. We use reachability graphs to argue that our approach preserves the behavior of the activity. Additionally, we applied the approach to a real system described by 36 activity diagrams. As a result 25 redundant instances were removed from 15 affected diagrams

Refactoring Haskell programs

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