Optimal control of finite source priority queues with computer system applications

The paper deals with the derivation of optimal control rules for finite source queueing systems with preemptive resume service discipline. The three performance measures considered are: server utilization, mean queue length and throughput.

It is indicated how the results on optimal control can be applied to multiprogrammed computer systems and some numerical examples are given.     

The 'Grand Challenge' in Informatics: Engineering Software-Intensive Systems

The science of information and information processing, informatics comprises many areas and includes principles of computing, storing, communicating, and visualizing information, and formalisms to describe information-processing procedures. The development and production of information-processing systems is based on software support systems such as software tools or product data repositories. Software and systems engineering is thus the key discipline for constructing information-processing systems. In particular, software and systems engineering addresses issues such as requirements engineering, architectural design, implementation, reliability engineering, and long-term maintenance. Developing a methodology for specifying and verifying software-intensive systems poses a grand challenge that a broad stream of research must address     

Allocation and analysis of reliability: multiple levels: system, subsystem, and module

We model the reliability allocation and prediction process across a hierarchical software system comprised of modules, subsystems, and system. We experiment in modeling complex reliability software systems using several software reliability models to test the feasibility of the process and to evaluate the accuracy of the models for this application. This is a subject deserving research and experimentation because this type of system is implemented in safety-critical projects, such as National Aeronautics and Space Administration (NASA) flight software modules, that we use in our experiments. Given the reliability requirement of a software system in the software planning or design stage, we predict each module’s reliability and their relationships (e.g., reliability interactions among modules, subsystems, and system), Our critical interfaces and components are failure-mode sequences and the modules that comprise these sequences, respectively. In addition, we evaluate how sensitive the achievement of reliability goals is to predicted component reliabilities that do not meet expectations.     

Virtual network transport protocols for Myrinet

Bringing direct and protected network multiprogramming into mainstream cluster computing requires innovations in three key areas: application programming interfaces, network virtualization systems, and lightweight communication protocols for high-speed interconnects. The AM-II API extends traditional active messages with support for client-server computing and facilitates the construction of parallel clients and distributed servers. Our virtual network segment driver enables a large number of arbitrary sequential and parallel applications to access network interface resources directly in a concurrent but fully protected manner. The NIC-to-NIC communication protocols provide reliable and at-most-once message delivery between communication endpoints. The NIC-to-NIC protocols perform well as the number of endpoints and the number of hosts in the cluster are scaled. The flexibility afforded by the underlying protocols enables a diverse set of timely research efforts. Other Berkeley researchers are actively using this system to investigate implicit techniques for the coscheduling of communicating processes, an essential part of high-performance communications in multiprogrammed clusters of uni- and multiprocessor servers. Other researchers are extending the active message protocols described here for clusters of symmetric multiprocessors, using so-called multiprotocol techniques and multiple network interfaces per machine     

Software Engineering

The state of software engineering is diverse, disorderly, and expanding, Coined less than seven years ago, the term is used today to describe such disparate activities as programming methodology, software development, and programming tools and standards. But for all the confusion surrounding it, this new discipline does seem to promise solutions to some of the most vexing problems of modern software development efforts: reliability and complexity. Clearly, the subject deserves to be explored.     

Reduced GUI for an interactive geometry software: Does it affect students' performance?

PurposeThe purpose of this paper is to describe an experimental study to reduce cognitive load and enhance usability for interactive geometry software.Design/methodology/approachThe Graphical User Interface is the main mechanism of communication between user and system features. Educational software interfaces should provide useful features to assist learners without generate extra cognitive load. In this context, this research aims at analyzing a reduced and a complete interface of interactive geometry software, and verifies the educational benefits they provide. We investigated whether a reduced interface makes few cognitive demands of users in comparison to a complete interface. To this end, we designed the interfaces and carried out an experiment involving 69 undergraduate students.FindingsThe experimental results indicate that an interface that hides advanced and extraneous features helps novice users to perform slightly better than novice users using a complete interface. After receiving proper training, however, a complete interface makes users more productive than a reduced interface.Originality/valueIn educational software, successful user interface designs minimize the cognitive load on users; thereby users can direct their efforts to maximizing their understanding of the educational concepts being presented.     

Hierarchical multi-level computer network for laboratory automation

The design and implementation of a microcomputer network to support laboratory automation is described and discussed. It is a multi-level hierarchical star network connected to a multiprogrammed computer on which all program development is done. The system is capable of supporting a large number of experimental setups. The microcomputers are either used as (1) local microcomputers for experiment control, (2) multiplexers for other microcomputers or (3) controllers for peripherals known in the multiprogrammed computer. The system combines the advantages of a large multiprogrammed computer with those of a small cheap dedicated computer close to the experiment. Character-oriented peripherals are connected to the multiprogrammed computer only. This reduces the amount of system software to be written for the network by an order of magnitude and eliminates the need for interfacing to existing small computer software. The system software consist of three small programs (monitors) providing a process concept and multibuffering of data in the involved computers. The monitor establishes a hierarchy of control and they eliminate the need for any local load device for the microcomputers as their monitors are in a read-only store. The system developed is designed for control of experiments in an environment where the experiments and the control strategies change with time and where the data refinement required is beyond what can be done on the present generation of microcomputers.     

A design flow for supporting component-based software development in multiprocessor real-time systems

Component-based software development established as an effective technique to cope with the increasing complexity of modern computing systems. In the context of real-time systems, the M-BROE framework has been recently proposed to efficiently support component-based development of real-time applications on multiprocessor platforms in the presence of shared resources. The framework relies on a two-stage approach where software components are first partitioned upon a virtual multiprocessor platform and are later integrated upon the physical platform by means of component interfaces that abstract from the internal details of the applications. This work presents a complete design flow for the M-BROE framework. Starting from a model of software components, a first method is proposed to partition applications to virtual processors and perform a synthesis of multiple component interfaces. Then, a second method is proposed to support the integration of the components by allocating virtual processors to physical processors. Both methods take resource sharing into account. Experimental results are also presented to evaluate the proposed methodology.     

Software Engineering for User Interfaces

The discipline of software engineering can be extended in a natural way to deal with the issues raised by a systematic approach to the design of human-machine interfaces. Two main points are made: that the user should be treated as part of the system being designed, and that projects should be organized to take account of the current (small) state of a priori knowledge about how to design interfaces.     

A structured methodology for comparative evaluation of user interface designs using usability criteria and measures

Previous research in software ergonomics has indicated the importance of evaluating the usability of computer user interfaces. This paper presents a quantitative basis for selecting from among multiple alternative interfaces relative to multiple criteria of usability concern. The proposed model consists of two main phases: the prescreening phase and the evaluation phase. The prescreening phase involves expert judgment-based assessment with qualitative criteria. The first phase uses absolute measurement analytic hierarchy process (AHP) to filter possible alternative interfaces to a reasonable subset. The evaluation phase involves user-based assessment such as user testing, with quantitative criteria. The objective of the second phase is to evaluate a subset of alternatives using objective measures and to select the best alternative. A set of criteria and measures for evaluating the usability of computer software designs is presented. The proposed methodology is demonstrated in the interface design of a database system used to analyze trip cases information of nuclear power plant.Relevance to industry

There is currently a focus on the usability of interactive computer software. Software developers, interface designers or human factors engineers often confront the task of comparative evaluation among systems, versions or interface designs. The proposed methodology provides practitioners with a structured approach to select the best interface based on usability criteria and measures.     

基于模糊重用库的容错软件开发

容错设计是改进软件可靠性的有效途径，然而由于设计多样性的实现很困难且开销大，导致该项技术目前仅应用于一些安全关键系统之中，为此，提出了一种将重用技术引入到容错软件开发过程中的应用框架，框架以模糊重用库为核心，增强的可靠性开发模型为基础，参数化可靠性指标为相异性设计的依据，简化了容错软件的开发过程，在方法和实践上改进了软件系统的可靠性，介绍了重用库结构，增强的可靠性开发方法，基于重用的相异性设计及其容错软件开发的支持。     

On the reliability of AI planning software in real-timeapplications

We define the reliability of a real-time system incorporating AI planning programs as the probability that, for each problem-solving request issued from the environment, the embedded system can successfully plan and execute a response within a specified real-time deadline. A methodology is developed for evaluating the reliability of such systems taking into consideration the fact that, other than program bugs, the intrinsic characteristics of AI planning programs may also cause the embedded system to fail even after all software bugs are removed from the program. The utility of the methodology is demonstrated by applying it to the reliability evaluation of two AI planning algorithms embedded in a real-time multicriteria route finding system     

Software development for reliable software systems

The process of software development has a major influence on the reliability of a software system. The reliability of a software system can be improved by eliminating all the errors that occur during its development. This paper presents, from a tutorial point of view, a methodology of software development that can minimize the number of errors in a system when the system is being developed. The three phases of software development viz. requirements analysis, design, and implementation are examined to find out what needs to be done in each phase, how the end result of each phase can be verified for correctness, and how the form in which information is passed between each phase can be improved. This discussion is directly applicable to the development of small software systems and programs.     

Principles of Built-In-Test for Run-Time-Testability in Component-Based Software Systems

This paper examines the motivations and expectations of Built-In-Test (BIT) techniques for Run-Time-Testability (RTT) in component-based software systems. The difficulties associated with testing and integrating fully encapsulated components lead to a requirement for testing interfaces. The format of these interfaces is explored at a high level of abstraction, and some possibilities for Built-In-Test (BIT) are described. BIT is concerned with the detection of error conditions arising internally to a component, or arising from erroneous component interactions, and the propagation of these error conditions to a system component having responsibility for error handling and/or recovery. The implications for testability, reliability and maintainability are discussed, and it is concluded that BIT offers potential for improved product quality. Whilst the proposed approach is considered appropriate for a wide range of software systems, issues related to real-time systems, such as deadlock and timing constraints are of particular interest.     

基于VxWorks的高可靠性网络通信研究

基于Windows的以太网的商业应用环境,不适合高科技领域网络通信对强实时性和高可靠性的需求.针对上述问题,研究了在嵌入式实时操作系统VxWorks的支持下,如何设计一个双网冗余备份的高可靠性网络.论述了这种网络的拓扑结构,通信协议,报文格式及其相关软件接口.实践结果表明,该网络完全满足特殊应用对象的强实时、高可靠性要求,     

Implementation of a human-friendly systems methodology for intelligent control system modelling and simulation

We have been developing an interactive computer software for the systematic support to modeling and simulation of intelligent control systems, based on a human-friendy systems methodology. The support system has a universal application in data analysis, system structuring, statistical and fuzzy modeling, and simulation, with the aid of human-computer interfaces to acquire knowledge or judgment of the domain experts. This paper presents our soft systems methodology and its implementation into the computer to develop intelligent process control systems. New technical proposals include a modeling method of fuzzy implication inference models and a design method of model predictive controllers.     

基于Petri网结构的多处理机实时操作系统

多处理机环境下的实时系统具有并发事件驱动性质,其软件结构展现了多重同步点以及生产者与消费者之间的关系,这导致了复杂的控制结构.对于此类系统软件的开发缺少标准的方法和工具,造成了软件低效、程序结构不清晰、开发成本高、维护困难的现象的出现.根据Petri网易于描述并行/并发现象的特点,采用它来解决多处理机软件的描述问题,介绍了一种以Petri网图形方式在多处理机系统环境下进行程序设计的方法.该方法基于两种程序设计级别:任务级和作业级.前者负责描述基本操作,由单一控制线程完成;后者用于并行/并发程序建模,由整个多处理机系统来执行.在作业级程序设计中,用户采用面向对象Petri网来描述并行程序结构,以建立系统模型.该方法以一种接近于程序员的思维方式去设计并发软件,提供了一种可靠的并行结构的程序.阐述了支持此种程序设计方法的操作系统结构及其实现原理.