Segue: support for distributed graphical interfaces

The authors describe their experiences developing Segue, an interface tool for supporting application programs that manipulate tree-like data structures. This semantic domain, although restrictive, includes a number of important application programs, such as structured editors, incremental compilers, and file system managers. The user interface tools described here support the Distributed Ada Programming Support Environment (DAPSE). The authors discuss the structure of Segue, present the R2D unparsing system, and examine tree-to-tree mappings. They then present three Segue user interfaces: an Ada editor, an Ada library manager, and the Gift interface specification tool     

Architectural support for efficient multicasting in irregularnetworks

Parallel computing on networks of workstations is fast becoming a cost-effective high-performance computing alternative to MPPs. Such a computing environment typically consists of processing nodes interconnected through a switch-based irregular network. Many of the problems that were solved for regular networks have to be solved anew for these systems. One such problem is that of efficient multicast communication. In this paper, we propose two broad categories of schemes for efficient multicasting in such irregular networks: network interface-based (NI-based) and switch-based. The NI-based multicasting schemes use the network interface of intermediate destinations for absorbing and retransmitting messages to other destinations in the multicast tree. In contrast, the switch-based multicasting schemes use hardware support for packet replication at the switches of the network and a concept known as multidestination routing to convey a multicast message from one source to multiple destinations. We first present alternative schemes for efficient multipacket forwarding at the NI and derive an optimal k-binomial multicast tree for multipacket NI-based multicast. We then propose two switch-based multicasting schemes that differ in the power of the encoding scheme and the complexity of the decoding logic at the switches. These multicasting schemes use path-based multidestination worms that can cover all nodes connected to switches along a valid unicast path and tree-based multidestination worms that can cover entire destination sets in a single phase using one worm, respectively. For each scheme, we describe the associated header encoding and decoding operation, the method for deriving multidestination worms that cover arbitrary multicast destination sets, and the multicasting scheme using the derived multidestination worms     

Architectural support for designing fault-tolerant open distributedsystems

An overview of the main techniques for designing fault-tolerant software and hardware systems is provided. The important features of the building blocks (computers, memories, buses, etc.) that can support an efficient implementation of fault-tolerant open distributed systems (FTODSs) are identified. Taking into account the features of these building blocks, an organization for FTODS is proposed. A distributed voting algorithm and a two-level hierarchy for permanent memory are key elements in this scheme. The algorithms needed for transferring files and synchronizing the concurrent activities of the computing modules and for recovery-are ISO standard protocols. Low-level voting and recovery algorithms that can run as a layer of software above the operating system make the open distributed system an attractive environment for applying fault-tolerant techniques     

Efficiently support concurrent queries in multiuser CBIR systems

Various techniques have been developed for different query types in content-based image retrieval systems such as sampling queries, constrained sampling queries, multiple constrained sampling queries, k-NN queries, constrained k-NN queries, and multiple localized k-NN queries. In this paper, we propose a generalized query model suitable for expressing queries of different types, and investigate efficient processing techniques for this new framework. We exploit sequential access and data sharing by developing new storage and query processing techniques to leverage inter-query concurrency. Our experimental results, based on the Corel dataset, indicate that the proposed optimization can significantly reduce average response time in a multiuser environment, and achieve better retrieval precision and recall compared to two recent techniques.

Architectural support for thread communications in multi-core processors

In the ongoing quest for greater computational power, efficiently exploiting parallelism is of paramount importance. Architectural trends have shifted from improving single-threaded application performance, often achieved through instruction level parallelism (ILP), to improving multithreaded application performance by supporting thread level parallelism (TLP). Thus, multi-core processors incorporating two or more cores on a single die have become ubiquitous. To achieve concurrent execution on multi-core processors, applications must be explicitly restructured to exploit parallelism, either by programmers or compilers. However, multithreaded parallel programming may introduce overhead due to communications among threads. Though some resources are shared among processor cores, current multi-core processors provide no explicit communications support for multithreaded applications that takes advantage of the proximity between cores. Currently, inter-core communications depend on cache coherence, resulting in demand-based cache line transfers with their inherent latency and overhead. In this paper, we explore two approaches to improve communications support for multithreaded applications. Prepushing is a software controlled data forwarding technique that sends data to destination’s cache before it is needed, eliminating cache misses in the destination’s cache as well as reducing the coherence traffic on the bus. Software Controlled Eviction (SCE) improves thread communications by placing shared data in shared caches so that it can be found in a much closer location than remote caches or main memory. Simulation results show significant performance improvement with the addition of these architecture optimizations to multi-core processors.     

Hypermedia-based support for cooperative learning of process knowledge

The WWW makes learning materials widely accessible and provides an environment where people can learn across time and space. However, the simple read-only information structure on the Web provides little or very limited guidance to learners, especially when they want to learn how to do something through interaction with computers and other people. We suggest overcoming the problem by introducing a graphical hypermedia-based process representation and a cooperative process enactment support. The hypermedia-based process structure is accessible on the WWW. It contains a rich set of associated materials with which people can seamlessly interact while they are systematically carrying out the process they are learning under the guidance of computers or tutors. A hypermedia-based process support system and two use cases are presented. The use cases show that such a system can not only provide traditional learning support, but also offers novel cooperative hypermedia based support for the learning of process knowledge.     

Flexible support for business processes: extending cooperative hypermedia with process support

In this paper, we present a cooperative hypermedia-based process support system focusing on flexible business processes. An analysis of the communication, coordination and cooperation requirements of business processes reveals a gap in current computer support. We propose to address these requirements by extending a cooperative hypermedia system with process support. The resulting system, called CHIPS, uses hypermedia-based activity spaces to model the structural, relational, and computational semantics of both individual tasks and processes. Application examples demonstrate that the CHIPS system retains the intuitive usability of hypertext and can support a wide range of business processes.     

Component interfaces that support measurement uncertainty

A method for designing modular instrumentation systems that can propagate measurement uncertainty is described. The approach adheres to current international best-practice in uncertainty calculation, as presented in the “Guide to the Expression of Uncertainty in Measurement” [International Organization for Standardization, Geneva, 1995]. System components fully encapsulate implementation details and a standardized interface can be used for inter-module communication. The method offers a convenient conceptual framework for design, providing automatic uncertainty evaluation, as well as simplified testing and validation.     

Architectural support for goal management in flat concurrent Prolog

A special-purpose architectural support that reduces the goal-management execution time in flat concurrent Prolog (FCP) is described. The architectural support consists of a dedicated goal-management unit that executes high-level goal-management operations concurrently with goal-reduction operations. The efficient execution of goal-management instructions is realized using a goal cache that stores recently spawned goals. It is shown that operations such as goal-switching, spawning, and halting are efficiently performed by changing their status in the goal cache. More complex operations, such as goal suspension and activation are decoupled from goal reduction by using two suspension tables and activation queues. Using an analytic performance model, it is shown that, for the systems development workload, which consists of large FCP programs, the overhead of software-implemented goal management is 50% of the program execution time. This is reduced up to 3% using the goal-management unit and the goal cache, resulting in a speedup of almost 2. The results are generalized for other workloads that exhibit different goal-management complexities     

Architectural support for inter-stream communication in an MSIMD system

This paper considers hardware support for the exploitation of control parallelism on data parallel architectures. It is well known that data parallel algorithms may also possess control parallel structure. However, the splitting of control leads to data dependency and synchronization issues that were implicitly handled in conventional SIMD architectures. These include synchronization of access to scalar and parallel variables, and synchronization for parallel communication operations. We propose a sharing mechanism for scalar variables and identify a strategy which allows synchronization of scalar variables between multiple streams. The techniques considered are based on a bit-interleaved register file structure which allows fast copy between register sets. Hardware cost estimates and timing analyses are provided, and comparison with an alternate scheme is presented. The register file structure has been designed and simulated for the HP 0.8μm CMOS process, and circuit simulation indicates access times are less than six nanoseconds. In addition, the impact of this structure on system performance is also studied.     

Multiple views system to support awareness for cooperative design

It is acknowledged that multiple views technology improves designer’s work efficiency by filtering redundant information. However, the increased need of cooperative activities in product design process requires views incorporating Cooperative awareness information (CAI), content of which should be lean for understanding and sortable according to importance. To achieve this target, this paper proposes an Object-based cooperative awareness model (OBCWM) and corresponding multiple views system. Requirements of CAI in product design are firstly analyzed. Then OBCWM is proposed, which consists of a CPM (Core product model) based concept framework. By use of CPM, an algorithm to calculate awareness intensity is developed based on object-oriented method. To support the mechanism of OBCWM, a multiple views system is then designed with “flexible view”, content of which is adjustable according to awareness intensity between CAI objects. After introduction to the system, application on a case is presented, followed by the evaluation of this system.     

Garnet: comprehensive support for graphical, highly interactiveuser interfaces

The Garnet research project, which is creating a set of tools to aid the design and implementation of highly interactive, graphical, direct-manipulation user interfaces, is discussed. Garnet also helps designers rapidly develop prototypes for different interfaces and explore various user-interface metaphors during early product design. It emphasizes easy specification of object behavior, often by demonstration and without programming. Garnet contains a number of different components grouped into two layers. The Garnet Toolkit (the lower layer) supplies the object-oriented graphics system and constraints, a set of techniques for specifying the objects' interactive behavior in response to the input devices, and a collection of interaction techniques. On top of the Garnet Toolkit layer are a number of tools to make creating user interfaces easier. The components of both layers are described     

Basic support for cooperative work on the World Wide Web

The emergence and widespread adoption of the World Wide Web offers a great deal of potential in supporting cross-platform cooperative work within widely dispersed working groups. The Basic Support for Cooperative Work (BSCW) project at GMD is attempting to realize this potential through development of web-based tools which provide cross-platform collaboration services to groups using existing web technologies. This paper describes one of these tools, theBSCW Shared Workspace system—a centralized cooperative application integrated with an unmodified web server and accessible from standard web browsers. The BSCW system supports cooperation through “shared workspaces”; small repositories in which users can upload documents, hold threaded discussions and obtain information on the previous activities of other users to coordinate their own work. The current version of the system is described in detail, including design choices resulting from use of the web as a cooperation platform and feedback from users following the release of a previous version of BSCW to the public domain.     

Motion support during the swing phase using cooperative walking support system

Walking support systems have been developed for supporting the motion of the elderly and physically disabled. In this research, we propose a walking support system based on the cooperation between wearable-type and cane-type walking support systems for supporting hemiplegic patients with disabilities. The system is controlled based on the intended motion of the user, their state and environmental information. In this system, we aim to realize several functions for supporting the daily life of the user by cooperatively controlling each walking support systems including walking support, sit-to-stand assistance, navigation, fall prevention and so on. As the first step to build this system, we focus on the walking support in this paper. For realizing the walking support, we propose a wearable-type walking support system that assists leg motion during the swing phase based on the motion of a cane-type walking support system moved by the user.     

Extending objects to support multiple interfaces and access control

A mechanism, called views, that allows programmers to specify multiple interfaces for objects and to control explicitly access to each interface is described. This mechanism provides a simple and flexible means of specifying enforceable access restrictions at many levels of granularity. It also results in system organization that supports browsing based on a number of different criteria. Views is defined, some examples of its uses are given, the impact of views on system organization is discussed, and five approaches to implementing views are outlined     

Requirements for community support systems - modularization,integration and ubiquitous user interfaces

Community support platforms are gaining more and more interest in areas ranging from leisure support and customer support in electronic commerce to knowledge management in enterprises. However, current solutions usually are built as proprietary systems or as add-ons to systems designed for other purposes. The platforms are usually not very customizable and interoperable and are not utilizing the full potential of the community support idea. We have introduced community platforms in several domains and have derived some requirements in these projects. These requirements are mainly related to different aspects of usability. In this paper we present the requirements and motivate an architecture for community support systems designed to fulfil these requirements.     

Requirements for community support systems - modularization, integration and ubiquitous user interfaces

Community support platforms are gaining more and more interest in areas ranging from leisure support and customer support in electronic commerce to knowledge management in enterprises. However, current solutions usually are built as proprietary systems or as add-ons to systems designed for other purposes. The platforms are usually not very customizable and interoperable and are not utilizing the full potential of the community support idea. We have introduced community platforms in several domains and have derived some requirements in these projects. These requirements are mainly related to different aspects of usability. In this paper we present the requirements and motivate an architecture for community support systems designed to fulfil these requirements.     

Anytime mining for multiuser applications

Database systems have been designed to serve multi-users in real-world applications. There are essential differences between mono- and multi-user applications when a database is very large. Therefore, this paper presents an "anytime" framework for mining very large databases which are shared by multi-users. Anytime mining is designed to generate approximate results such that these results can be accessed at any time while the system is autonomously mining a database.     

A cooperative information system to support multi-expert systems development

The development of a multi-expert system (MES) is obviously a team project. This paper shows how database technology can actively and cooperatively support the development and design of a multi-expert system. The proposed solution is based on an Active and Deductive DataBase (ADDB). An extensional database records and maintains information about the project and its evolution. An intensional database, defined by a set of rules, coordinates and controls the activity of the different actors, and models relevant views on the project. This rule base can be fired automatically when an interesting event occurs and consequently either informs the members of the team concerned by this event (beginning of a new step, creation of a new product, modification of a knowledge base, etc.), or triggers another activity, or invokes other tools. This rule base can also be executed explicitly to provide its user (experts, developers, the project manager, etc.) with cooperative information concerning the project. This cooperative information improves the visibility and the intelligibility of the project and knowledge reuse.     

基于组件的分布式软件的动态配置和容错

论文提出一种结构化新方法,它能通过动态配置支持基于组件的分布式软件的容错。采用面向图形的编程模型,基于组件的分布式软件的软件体系结构可用一个逻辑图来表示,该逻辑图可以精化为一个明确的对象并分布到网络中,软件的动态配置通过执行定义在图上的一系列操作来实现,发生错误时通过动态重配置软件来支持容错。论文描述了该方法的基本模型、系统结构及其在CORBA上的实现原型。