Sonderforschungsbereich 501
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1998,4
In order to improve the quality of software systems and to set up a more effective process for their development, many attempts have been made in the field of software engineering. Reuse of existing knowledge is seen as a promising way to solve the outstanding problems in this field. In previous work we have integrated the design pattern concept with the formal design language SDL, resulting in a certain kind of pattern formalization. For the domain of communication systems we have also developed a pool of SDL patterns with an accompanying process model for pattern application. In this paper we present an extension that combines the SDL pattern approach with the experience base concept. This extension supports a systematic method for empirical evaluation and continuous improvement of the SDL pattern approach. Thereby the experience base serves as a repository necessary for effective reuse of the captured knowledge. A comprehensive usage scenario is described which shows the advantages of the combined approach. To demonstrate its feasibility, first results of a research case study are given.
1999,4
Using an experience factory is one possible concept for supporting and improving reuse in software development. (i.e., reuse of products, processes, quality models, ...). In the context of the Sonderforschungsbereich 501: "Development of Large Systems with Generic methods" (SFB501), the Software Engineering Laboratory (SE Lab) runs such an experience factory as part of the infrastructure services it offers. The SE Lab also provides several tools to support the planning, developing, measuring, and analyzing activities of software development processes. Among these tools, the SE Lab runs and maintains an experience base, the SFB-EB. When an experience factory is utilized, support for experience base maintenance is an important issue. Furthermore, it might be interesting to evaluate experience base usage with regard to the number of accesses to certain experience elements stored in the database. The same holds for the usage of the tools provided by the SE LAB. This report presents a set of supporting tools that were designed to aid in these tasks. These supporting tools check the experience base's consistency and gather information on the usage of SFB-EB and the tools installed in the SE Lab. The results are processed periodically and displayed as HTML result reports (consistency checking) or bar charts (usage profiles).
1999,8
Comprehensive reuse and systematic evolution of reuse artifacts as proposed by the Quality Improvement Paradigm (QIP) do not only require tool support for mere storage and retrieval. Rather, an integrated management of (potentially reusable) experience data as well as project-related data is needed. This paper presents an approach exploiting object-relational database technology to implement the QIP-driven reuse repository of the SFB 501. Requirements, concepts, and implementational aspects are discussed and illustrated through a running example, namely the reuse and continuous improvement of SDL patterns for developing distributed systems. Based on this discussion, we argue that object-relational database management systems (ORDBMS) are best suited to implement such a comprehensive reuse repository. It is demonstrated how this technology can be used to support all phases of a reuse process and the accompanying improvement cycle. Although the discussions of this paper are strongly related to the requirements of the SFB 501 experience base, the basic realization concepts, and, thereby, the applicability of ORDBMS, can easily be extended to similar applications, i. e., reuse repositories in general.
1998,7
The notion of formal description techniques for timed systems (T-FDTs) has been introduced in [EDK98a] to provide a unifying framework for description techniques that are formal and that allow to describe the ongoing behavior of systems. In this paper we show that three well known temporal logics, MTL, MTL-R , and CTL*, can be embedded in this framework. Moreover, we provide evidence that a large number of dioeerent kinds of temporal logics can be considered as T-FDTs.
1999,11
Struktur und Werkzeuge des experiment-spezifischen Datenbereichs der SFB501 Erfahrungsdatenbank
(1999)
Software-Entwicklungsartefakte müssen zielgerichtet während der Durchführung eines Software- Projekts erfasst werden, um für die Wiederverwendung aufbereitet werden zu können. Die methodische Basis hierzu bildet im Sonderforschungsbereich 501 das Konzept der Erfahrungsdatenbank. In ihrem experiment-spezifischen Datenbereich werden für jedes Entwicklungsprojekt alle Software-Entwicklungsartefakte abgelegt, die während des Lebenszyklus eines Projektes anfallen. In ihrem übergreifenden Datenbereich werden all die jenigen Artefakte aus dem experiment-spezifischen Datenbereich zusammengefasst, die für eine Wiederverwendung in nachfolgenden Projekten in Frage kommen. Es hat sich gezeigt, dass bereits zur Nutzung der Datenmengen im experiment- spezifischen Datenbereich der Erfahrungsdatenbank ein systematischer Zugriff notwendig ist. Ein systematischer Zugriff setzt jedoch eine normierte Struktur voraus. Im experiment-spezifischen Bereich werden zwei Arten von Experimenttypen unterschieden: "Kontrollierte Experimente" und "Fallstudien". Dieser Bericht beschreibt die Ablage- und Zugriffsstruktur für den Experimenttyp "Fallstudien". Die Struktur wurde aufgrund der Erfahrungen in ersten Fallstudien entwickelt und evaluiert.
1996,15
A non-trivial real-time requirement obeying a pattern that can be foundin various instantiations in the application domain building automation, and which is therefore called generic, is investigated in detail. Starting point is a description of a real-time problem in natural language augmented by a diagram, in a style often found in requirements documents. Step by step, this description is made more precise and finally transformed into a surprisingly concise formal specification, written in real-time temporal logic with customized operators. Wereason why this formal specification precisely captures the original description- as far as this is feasible due to the lack of precision of natural language.
1997,2
This paper discusses the benefits and drawbacks of caching and replication strategies in the WWW with respect to the Internet infrastructure. Bandwidth consumption, latency, and overall error rates are considered to be most important from a network point of view. The dependencies of these values with input parameters like degree of replication, document popularity, actual cache hit rates, and error rates are highlighted. In order to determine the influence of different caching and replication strategies on the behavior of a single proxy server with respect to these values, trace-based simulations are used. Since the overall effects of such strate- gies can hardly be decided with this approach alone, a mathematical model has been developed to deal with their influence on the network as a whole. Together, this two-tiered approach permits us to propose quantita- tive assessments on the influence different caching and replication proposals (are going to) have on the Inter- net infrastructure.
1996,19
Due to the large variety of modern applications and evolving network technologies, a small number of general-purpose protocol stacks will no longer be sufficient. Rather, customization of communication protocols will play a major role. In this paper, we present an approach that has the potential to substantially reduce the effort for designing customized protocols. Our approach is based on the concept of design patterns, which is well-established in object oriented software development. We specialize this concept to communication protocols, and - in addition - use formal description techniques (FDTs) to specify protocol design patterns as well as rules for their instantiation and composition. The FDTs of our choice are SDL-92 and MSCs, which offer suitable language support. We propose an SDL pattern description template and relate pattern-based configuring of communication protocols to existing SDL methodologies. Particular SDL patterns and the configuring of a customized resource reservation protocol are presented in detail.
1996,9
Ziel dieser Arbeit ist es, eine Methode zur Verfügung zu stellen, mit der ein Simulator für gebäudespezifische Aufgaben modelliert werden kann. Die Modellierung muß dabei so angelegt sein, daß sowohl einfache als auch sehr komplexe Simulatoren für spezielle Gebäude entworfen werden können. Aus dem erstellten Modell ist es anschließend möglich, mit Hilfe von Generatoren automatisch ein Programm zu erzeugen. Dadurch kann ein Entwerfer ohne spezielle Kenntnisse auf dem Gebiet der Simulation einen Gebäude-Simulator entwickeln. Zur Modellierung wurde ein domänenspezifischer Katalog von Entwurfsmustern erstellt. Dabei können die einzelnen Muster direkt zur Modellierung und Codegenerierung eingesetzt werden.
1996,14
The purpose of this expose is to explain the generic design of a customized communication subsystem. The expose addresses both functional and non-functional aspects. Starting point is a real-time requirement from the application area building automation. We show how this application requirement and some background information about the application area lead to a system architecture, a communication service, a protocol architecture and to the selection, adaptation, and composition of protocol functionalities. The reader will probably be surprised how much effort is necessary in order to implement the innocuous, innocent, inconspicuous looking application requirement. Formal description techniques (FDTs) will be used in all design phases.