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Scheduling algorithms that use application and system knowledge have been shown to be more effective at scheduling parallel jobs on a multiprocessor than algorithms that do not. This paper focuses on obtaining such information for use by a scheduler in a network of workstations environment. The log files from three parallel systems are examined to determine both how to categorize parallel jobs for storage in a job database and what job information would be useful to a scheduler. A Historical Profiler is proposed that stores information about programs and users, and manipulates this information to provide schedulers with execution time predictions. Several preemptive and non-preemptive versions of the FCFS, EASY and Least Work First scheduling algorithms are compared to evaluate the utility of the profiler. It is found that both preemption and the use of application execution time predictions obtained from the Historical Profiler lead to improved performance.

We present a general model of software development environments that consists of three components: structures, mechanisms and policies. The advantage of this model is that it distinguishes intuitively those aspects of an environment that are useful in comparing and contrasting software development environments. Our initial application of the model is to characterize four classes of environments by means of a sociological metaphor based on scale: the individual, the family, the city and the state models. The utility of the IFCS taxonomy is that it delineates the important classes of interactions among software developers and exposes the ways in which current software development environments inadequately support the development of large systems. We demonstrate the generality of our model by also applying it to a previously published taxonomy that categorizes environments according to how they relate to four historical trends: language-centered, structure-oriented, toolkit and method-bas...

This chapter surveys extended transaction models proposed to support long duration, interactive and/or cooperative activities in the context of multi-user software development and CAD/CAM environments. Many of these are variants of the checkout model, which addresses the long duration and interactive nature of the activities supported by environments but still isolates environment users, making it difficult for them to collaborate while their activities are in progress. However, a few cooperative transaction models have been proposed to facilitate collaboration, usually while maintaining some guarantees of consistency.

The areas of application of hypermedia technology, combined with the capabilities that hypermedia provides for manipulating structure, create an environment in which version control is very important. A hypermedia version control framework has been designed to specifically address the version control problem in open hypermedia environments. One of the primary distinctions of the framework is the partitioning of hypermedia version control functionality into intrinsic and application-specific categories. The version control framework has been used as a model for the design of version control services for a hyperbase management system that provides complete version support for both data and structural entities. In addition to serving as a version control model for open hypermedia environments, the framework offers a clarifying and unifying context in which to examine the issues of version control in hypermedia.

In the paper, the question of effective automated version selection is tackled. It is an important part of a method for building a software configuration. The paper concentrates on the method for version selection which allows specifying requirements which refer to properties of versions. It is controlled by knowledge in form of heuristic functions serving as necessary condition and suitability condition for selection. We present the method and describe its application in selecting software components. Keywords: software configuration management, version control, selection controlled by heuristics 1 Introduction The problem of version selection is a topic of much interest in the recent research within the area of software configuration management. Solving it is important for achieving quality of the configuration being built, but it also influences efficiency of the process of building a software system configuration. Requirements for version selection can have various forms: ffl a...

The program Amoeba Make, or Amake, is being designed to fulfil the need of a make-like configuration manager capable of exploiting the potentials of the Amoeba distributed operating system. The major design goal is to create a software configuration manager that is both easy to use and efficient. The specification and maintenance of a large configuration should be easy, and should be automated as much as possible. Furthermore, the build process should exploit Amoeba's capabilities and resources when creating or updating a target. In this paper we show how a smart file server can contribute to Amake's efficiency. We also show how a declarative configuration description allows Amake to take full advantage of parallelism and to determine the commands needed for building and maintaining targets. 1. INTRODUCTION The program Amake was designed to fulfil the need of a make-like configuration manager that tries to overcome make's inability to maintain large and complex systems in a convenien...

The paper describes a configuration language called PCL which has been designed to describe the architecture of multiple versions of computer-based systems. PCL is compared with other configuration languages and its features are illustrated by example. The features of PCL which are discussed here are its ability to model hardware and software in an integrated way, its provision of multiple structured architectural views, its ability to model system variability and its integration with a number of structured design methods. A supporting toolset for PCL has been implemented and is briefly described. 1. Introduction A key problem in supporting the evolution of computer-based systems is the management of variability. As systems evolve, new versions are created. In general, these different versions of the system will share components. Some of these components will be stable across all versions. Others will vary depending on the specific requirements of a particular version. This variability...

Abstract. This paper reports on some practical work undertaken to assess the use of a formalised configuration language to support industrial system development and evolution. The language and supporting analysis and system generation tools are the main result of the PROTEUS 1 project. The work described is based on practical application of the PROTEUS approach in Stentofon, a Norwegian industrial company producing customized internal communications systems.

Abstract not found