Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

Browse

Author: search.filters.author.Baras, John S.Subject: search.filters.subject.databases

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Disseminating Updates to Mobile Clients
    (1998) Stathatos, Konstantinos; Roussopoulos, Nick; Baras, John S.; ISR; CSHCN
    In this paper, we address the problem of propagating data updates to alarge number of mobile clients. Typically, mobile clients operateautonomously, i.e., disconnected from data servers, for prolongedperiods of time relying on locally replicated corporate data (e.g.,database views, file systems). From time to time, they need to refreshtheir replicas with data changes registered at a central datarepository. We propose a hybrid approach for delivering these updatesto the clients. We use a broadcast channel to "cache on the air"fresh updates for as long as they are high on demand. At the sametime, any requests for older updates are individually serviced by theserver through a separate channel. The air-caching satisfies the bulkof clients' needs, increasing data throughput many-fold compared totraditional data delivery mechanisms. We describe a hierarchicalair-cache structure, and analyze the performance of broadcasting a logof committed updates. Based on that, we propose a technique thatdynamically modifies the contents and the structure of the air-cacheaccording to the number and the (dis)connection habits of the clients.Through extensive simulations, we demonstrate the adaptiveness,efficiency, and practicality of the proposed system even for verylarge client populations.
  • Thumbnail Image
    Item
    Integrated Product and Process Design Environment Tool for Manufacturing T/R Modules
    (1997) Karne, Ramesh K.; Lai, Hsing-Tsu; Dandekar, Swati V.; Baras, John S.; Ball, Michael O.; Bashyam, Sridhar; Trichur, Vinai S.; Karir, Manish; Kebede, Abraham; Williams, Jim; ISR; CSHCN
    We present a decision making assistant tool for integrated product and process design environment for manufacturing applications. Specifically, we target microwave modules which use Electro-mechanical components and require optimal solutions to reduce cost, improve quality, and gain leverage in time to market the product. This tool will assist the product and process designer to improve their productivity and also enable to cooperate and coordinate their designs through a common design interface. We consider a multiobjective optimization model that determines components and processes for a given conceptual designs for microwave modules. This model outputs a set of solutions that are Pareto optimal with respect to cost, quality, and other metrics. In addition, we identify system integration issues for manufacturing applications, and propose an architecture which will serve as a building block to our continuing research in virtual manufacturing applications.
  • Thumbnail Image
    Item
    Managing File Subsystem Data Streams for Databases on Networked Systems
    (1996) Gupta, Sandeep K.; Baras, John S.; Kelley, Stephen; Roussopoulos, Nick; ISR; CSHCN
    One important activity for networked database systems that distribute data across several workstations is moving data between the file and network subsystems. It is possible to create data streams in the operating system kernel. If provided on a system, they allow user level processes to request transfer of data without having t copy it into the user space. This is particularly useful for data whose content or format is not modified during the transfer. In this paper we present a conservative criterion for access and control for the management of such data streams for databases in a networked environment, and define the implementation requirements for achieving the criterion. The approach is to maintain at least the current level of access management. We define the specific implementation semantics that this criterion entails.

  • Thumbnail Image
    Item
    Integrating Tradeoff Analysis and Plan-Based Evaluation of Designs for Microwave Modules
    (1996) Trichur, Vinai S.; Ball, Michael O.; Baras, John S.; Hebbar, Kiran; Minis, Ioannis; Nau, Dana S.; Smith, Stephen J.J.; ISR
    Previously, we have described two systems, EDAPS and EXTRA, which support design and process planning for the manufacture of microwave modules, complex devices with both electrical and mechanical attributes. EDAPS integrates electrical design, mechanical design, and process planning for both mechanical and electrical domains. EXTRA accesses various component and process databases to help the user define design and process options. It then supports the user in choosing among these options with an optimization bases tradeoff analysis module.

    In this paper, we describe our current work towards the integration and enhancement of the capabilities of EDAPS and EXTRA. We integrate EXTRA's functionality with the initial design step of EDAPS. in the resultant system, the user, supported by an enhanced tradeoff analysis capability, can select and describe a promising preliminary design and process plan based on the analysis of a variety of alternatives from both an electrical and mechanical perspective. This preliminary design is then subjected top further analysis and refinement using existing EDAPS capabilities. In addition to the integration of these two systems, specific new functions have been developed, including tradeoff analysis over a much broader set of criteria, and the ability of the tradeoff module to query the process planner to determine costs of individual options.

  • Thumbnail Image
    Item
    Evaluation of Product and Process Design in Electronics
    (1992) McMahon, M.; Prasannappa, R.; Baras, John S.; Zhang, G.; Kebede, Abraham; Mendicino, P.; ISR
    This paper describes techniques and an implementation for managing costs and quality of electronics products during design. Emphasis is given to the development of an economic model to estimate the production costs at the assembly level. The unique feature of this system is to bring the experience of a manufacturing engineer, quality engineer, and cost controller into the hands of a designer. Such an early integration of manufacturing knowledge creates a concurrent engineering environment which improves product quality and reduces cost through careful monitoring of the design phase.