15 Fakultätsübergreifend / Sonstige Einrichtung
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Item Open Access Practical methods and tools for specification(1987) Ludewig, JochenThis is a course on specification. Since it is based on experiences in the field of software engineering. It applies primarily to software specifications. Many observations and reports indicate, however, that, from specification aspects, there is not much difference between information processing systems in general and software in particular. Therefore, most of this course applies also to system specification. In the first chapter, some fundamentals are discussed. These include the life cycle model and the distribution of costs over the various activities, some definitions, and a rationale for semi-formal specification. The second chapter provides a general outline of a specification system, whose desirable properties are deduced from the qualities of good specifications. In the third chapter, we present some typical specification systems. The primary goal is to show some typical features of such systems rather than to describe them in detail. The fourth chapter addresses management aspects. In chapter 5, some general conclusions are drawn. The appendix (chapter 6) contains a bibliography on specification, and a list of suppliers.Item Open Access A Bayesian network approach to assess and predict software quality using activity-based quality models(2009) Wagner, StefanAssessing and predicting the complex concept of software quality is still challenging in practice as well as research. Activity-based quality models break down this complex concept into more concrete definitions, more precisely facts about the system, process and environment and their impact on activities performed on and with the system. However, these models lack an operationalisation that allows to use them in assessment and prediction of quality. Bayesian Networks (BN) have been shown to be a viable means for assessment and prediction incorporating variables with uncertainty. This paper describes how activity-based quality models can be used to derive BN models for quality assessment and prediction. The proposed approach is demonstrated in a proof of concept using publicly available data.Item Open Access SQL/XNF - processing composite objects as abstractions over relational data(1993) Mitschang, Bernhard; Pirahesh, Hamid; Pistor, Peter; Lindsay, Bruce; Südkamp, NorbertAn extension to SQL, called the SQL extended normal form (XNF), is discussed. It enhances relational technology by a composite object facility, which comprises not only extraction of composite objects from existing databases but also efficient navigation and manipulation facilities provided by an appropriate application programming interface. The language itself allows sharing of the database among normal form SQL applications and composite object applications. It provides proper subsetting of the database and subsequent structuring, exploiting subobject sharing and recursion, all based on its powerful composite object constructor concept, which is closed under the language operations. XNF is integrated into the relational framework, thus benefiting from the available technology such as relational engine and query optimization.Item Open Access Extending the relational algebra to capture complex objects(1989) Mitschang, BernhardAn important direction in database research for non-standard applications (e.g. engineering or design applications) deals with adequate support for complex objects. Without doubt, the provision of network structures and shared subobjects as well as support for dynamic object definition and appropriate manipulation facilities is urgently needed for natural and accurate modeling as well as for efficient processing of the applications' objects. These concepts are the major concern of the molecule-atom data model (MAD model) and its molecule algebra which is introduced in this paper. They make the model stand out compared to the relational model and even to models limited to hierarchical and statically defined complex objects. By means of the molecule algebra a precise and complete specification of one conceivable kind of complex object processing and its inherent semantics is provided. Furthermore, this algebra is used as a sound basis to express the semantics of the high level query language MOL (molecule query language) that is able to deal with complex objects in a descriptive manner.Item Open Access Do code clones matter?(2009) Juergens, Elmar; Deißenböck, Florian; Hummel, Benjamin; Wagner, StefanCode cloning is not only assumed to inflate maintenance costs but also considered defect-prone as inconsistent changes to code duplicates can lead to unexpected behavior. Consequently, the identification of duplicated code, clone detection, has been a very active area of research in recent years. Up to now, however, no substantial investigation of the consequences of code cloning on program correctness has been carried out. To remedy this shortcoming, this paper presents the results of a large-scale case study that was undertaken to find out if inconsistent changes to cloned code can indicate faults. For the analyzed commercial and open source systems we not only found that inconsistent changes to clones are very frequent but also identified a significant number of faults induced by such changes. The clone detection tool used in the case study implements a novel algorithm for the detection of inconsistent clones. It is available as open source to enable other researchers to use it as basis for further investigations.Item Open Access Information structures and database support for solid modeling(1989) Härder, Theo; Hübel, Christoph; Mitschang, BernhardThe question we are going to investigate is how to map solid representations to DB structures and how to process this information efficiently. Starting from analytical representations based on analytical methods we discuss the use of constructive solid geometry and boundary representation models with various refinements. Furthermore, additional submodels (organizational, technological, physical) are considered in order to obtain an overall product model. This model representing all important aspects of a complex design object may serve to derive special object representations needed by existing engineering tools or by mathematical methods (e.g. finite elements). Today's DBMS are unable to meet the increasing requirements of engineering applications that would prefer to use a DBMS. To alter this situation, a new generation of DBMS architectures tailored to the demands of such enhanced applications have to be developed. As a consequence, the flexibility and expressiveness of data models as well as the handling of application objects must be greatly improved before interactive design work can be supported. We outline our data model concepts and architectural decisions to provide effective data management support. Our DBMS architecture consists of a neutral kernel part running on a server machine and an application layer tailored to solid modeling tasks which together with the application, i.e. the solid modeler is allocated to the workstation.Item Open Access Using PRIMA-DBMS as a testbed for parallel complex-object processing(1992) Hübel, Christoph; Mitschang, Bernhard; Gesmann, Michael; Grasnickel, Andreas; Käfer, Wolfgang; Schöning, Harald; Härder, TheoThe PRIMA-DBMS approach is explained by introducing PRIMA's architecture and query processing framework. The PRIMA-DBMS constitutes a testbed that is flexible enough to support evaluation and validation of quite a variation of different strategies for complex-object processing taking into account different parallelization levels and different hardware environments. Thus, PRIMA marks an important step towards our main research goal concerning measures for efficient complex-object processing: the measures that are in competition with each other are query optimization, query evaluation strategies, and massive storage, that all benefit from parallelism. The programming environment that supports the parallel DBMS processing is introduced with special emphasis on its ability for parametrization and configuration. A case study of the PRIMA testbed illustrates our first investigations and demonstrates a methodology for evaluation and tuning of PRIMA configurations.Item Open Access Stand der Forschung und Technik auf dem Gebiet der rechnerunterstützten Spezifikation von Prozessrechner-Software(1983) Ludewig, JochenDas Thema "Spezifikation" wurde von den Informatikern identifiziert und bearbeitet im Zusammenhang mit der Entdeckung des Gebietes "Software-Engineering". Dies gilt auch für die Spezifikation solcher Systeme, die nur teilweise aus Software bestehen oder bei denen die Unterscheidung zwischen Hard- und Software noch nicht gemacht wurde. Daher soll hier versucht werden, das Gebiet von der Software-Spezifikation her anzugehen. Nach einem kurzen Abriss der Motivation für Spezifikationssysteme und ihrer Geschichte werden die in diesem Zusammenhang wichtigen Begriffe diskutiert. Auch die übliche Einteilung des Software-Entstehungsprozesses, der "softwarelife-cycle", wird angesprochen. Für die einzelnen Komponenten der Spezifikationssysteme haben sich Lösungen herauskristallisiert, die in vielen Systemen zu finden sind. Diese werden gegenübergestellt und diskutiert. Dann werden der aktuelle Stand und die Trends skizziert. Am Schluss stehen einige Erfahrungssätze zur Einführung eines Spezifikationssystems.Item Open Access Abbildung von Frames auf neuere Datenmodelle(1987) Härder, Theo; Mattos, Nelson Mendonca; Mitschang, BernhardEs wird die Abbildung von Frames mit ihren Modellierungskonzepten und charakteristischen Operationen auf objektorientierte Datenmodelle untersucht, um Wissensrepräsentation in sogenannten Non-Standard-Datenbanksystemen - beispielsweise für Expertensystem-Anwendungen - unterstützen zu können. Nach einem Vergleich der Eigenschaften von Relationenmodell, NF 2-Modell und MAD-Modell für diese Aufgabe wird eine Bewertung der verschiedenen Ansätze vorgenommen, um ihre Tauglichkeit für die Frame-Modellierung deutlicher herauszukristallisieren.Item Open Access A model and sensitivity analysis of the quality economics of defect-detection techniques(2006) Wagner, StefanOne of the main cost factors in software development is the detection and removal of defects. However, the relationships and influencing factors of the costs and revenues of defect-detection techniques are still not well understood. This paper proposes an analytical, stochastic model of the economics of defect detection and removal to improve this understanding. The model is able to incorporate dynamic as well as static techniques in contrast to most other models of that kind. We especially analyse the model with state-ofthe-art sensitivity analysis methods to (1) identify the most relevant factors for model simplification and (2) prioritise the factors to guide further research and measurements.