Mario Winter

Coupling Use Cases and Class Models as a Means for Validation and Verification of Requirements Specifications

In many applications, especially from the business domain, the requirements specification mainly deals with use cases and class models. Unfortunately, these models are based on different modelling techniques and aim at different levels of abstraction, such that serious consistency and completeness problems are induced. To overcome these deficiencies, we refine activity graphs to meet the needs for a suitable modelling element for use case behaviour. The refinement in particular supports the proper coupling of use cases via activity graphs and the class model. The granularity and semantics of our approach allow for a seamless, traceable transition of use cases to the class model and for the verification of the class model against the use case model. The validation of the use case model and parts of the class model is supported as well. Experience from several applications has shown that the investment in specification, validation and verification not only pays off during system and acceptance testing but also significantly improves the quality of the final product.

Window query-optimal clustering of spatial objects

During the last decade various spatial data structures have been designed and compared against each other with respect to their performance. Still missing is a lower bound result, e.g. an optimal spatial data clustering, which would allow for the absolute comparison of the performance of the well-known data structures with the optimum. In this paper, we address the static situation where the data is known in beforehand. An optimal data clustering for this setting will also provide a lower bound for the dynamic situation where the input data is not known in advance and the data structure is built up by iterated insertions. Using as performance measure the expected number of data bucket accesses needed to perform a window query, the static clustering problem turns into a classical optimization problem. For the special case of bucket capacity cb = 2 the optimization problem is solvable in polynomial time, whereas for cb 3 it is NP-hard. In experiments using simulated annealing heuristics for the optimization the best dynamic structures as well as the static packed R-tree perform about 20% worse than the optimum on average. However, we again want to emphazise that we understand our contribution as lower bound result rather than another speed-up variant of classical spatial data structures.

Round-Trip Prototyping Based on Integrated Functional and User Interface Requirements Specifications

Requirements engineering in the new millennium is facing an increasing diversity of computerised devices comprising an increasing diversity of interaction styles for an increasing diversity of user groups. Thus the incorporation of user interface requirements into software requirements specifications becomes more and more mandatory. Validating these requirements specifications with hand-made, throw-away prototypes is not only expensive, but also bears the danger that validation results are not accurately fed back into the requirements specification. In this paper, we propose an enhancement of the requirements specification method SCORES for an explicit capturing of user interface requirements. The advantages of the approach are threefold. First, the user interface requirements specification is UML-compliant and integrated into the functional requirements specification. Second, prototypes for validation purposes can semi-automatically be generated. Third, the model-based generation of prototypes allows for ‘round-trip prototyping’ such that manual changes of the prototype during the validation process are automatically fed back into the requirements specification.

Ein interaktionsbasiertes Modell für den objektorientierten Integrations- und Regressionstest

Zusammenfassung. Bei der iterativen, inkrementellen Software-Entwicklung werden Klassen sukzessive spezifiziert, implementiert bzw. geändert oder erweitert, klassengetestet und zu einem ausführbaren Anwendungssystem integriert. Integrations- und Regressionstest stellen dabei besonders wichtige und häufig ausgeführte Testaktivitäten dar, die zudem aufgrund der vielfältigen Interaktionsmöglichkeiten in objektorientierten Programmen sehr komplex sind. Integrations- und Regressionstest werden in der Literatur stets separat behandelt, obwohl sie durchaus ähnliche Teilaktivitäten beinhalten. Bestehende Ansätze zum objektorientierten Integrationstest betrachten entweder strukturelle oder verhaltensorientierte Systembeschreibungen. In diesem Beitrag stellen wir das Klassen-Botschaftsdiagramm (KBD) vor, ein Struktur und Verhalten objektorientierter Programme gleichermaßen berücksichtigendes interaktionsbasiertes (Test-)Modell. Wir skizzieren Algorithmen zur Änderungsanalyse, Ableitung einer Integrationsstrategie und Auswahl von Regressionstestfällen nach der Modifikation bestehender Klassen. Abschließend werden die Ergebnisse einiger mit Smalltalk-80 Klassen durchgeführter Experimente zur Evaluierung des Verfahrens vorgestellt.Abstract. The highly incremental and iterative development cycle for object-oriented software demands both many changes and partially implemented resp. re-implemented classes. Much integration and regression testing has to be done to reach stable stages, which turned out to be considerably more complex than testing conventional software. Despite many similarities, integration and regression testing are treated separately in literature. Known integration testing techniques concentrate on either structural or behavioral descriptions of the system. In this presentation we propose the Class-Message Diagram (CMD), a diagram capturing all possible interactions in an object-oriented program. Then we sketch algorithms to identify integration resp. regression test strategies and all test cases to be executed after some implementation resp. modification activities. Finally, we summarize some experiments on Smalltalk-80 programs.

Kopplung von Anwendungsfällen und Klassenmodellen in der objektorientierten Anforderungsanalyse

In der UML-basierten objektorientierten Anforderungsanalyse werden funktionale Anforderungen mit Hilfe von Anwendungsfallen formuliert, ihre Dynamik z.B. durch Aktivitatsdiagramme modelliert und strukturelle Anforderungen durch Klassenmodelle beschrieben. Techniken und Abstraktionsniveaus der Teilmodelle sind sehr verschieden, so das sich erhebliche Konsistenzprobleme fur die Gesamtspezifikation ergeben. Um diese Nachteile zu uberwinden, erweitern und prazisieren wir Anwendungsfalle im Hinblick auf die Modellierung ihres dynamischen Verhaltens. Granularitat und Semantik des Ansatzes schliesen die Lucke zwischen Anwendungsfallen und Klassenmodellen und legen die Basis fur die Validierung von Anwendungsfallen und Teilen des Klassenmodells und die Verifikation des Klassenmodells gegen die Anwendungsfalle.