Language and Visualization Support for Large-Scale Concurrency

SDL (Shared Dataspace Language) is a language for writing and visualizing programs consisting of thousands of processes executing on a highly-parallel multiprocessor. SDL is based on a model in which processes use powerful transactions to manipulate abstract views of a virtual, content-addressable data structure called the dataspace. The process society is dynamic and supports varying degrees of process anonymity. The transactions are executed over abstract views of the dataspace. This facilitates elegant conceptualization of dataspace transformations and compact program representation. Processes and transactions enable SDL to combine elements of both large and fine grained concurrency. The view is a novel abstraction mechanism whose significance is derived from the fact that it allows processes to interrogate the dataspace at a level of abstraction convenient for the test they are pursuing. The view also plays a role in the definition of continuously updated, programmer-defined visual abstractions which enable exploration of the program\u27s functionality and performance

Concurrency Coordination in a Locally Distributed Database System

A pipelined architecture for a locally distributed database system is proposed along with a simple concurrency coordination mechanism. The approach is based on the idea of serializing transaction processing throughout the database. The scheme is shown to require few coordination messages, to be deadlock free, to preserve database consistency, and to support recovery. Several performance related issues are also discussed

A Taxonomy of Requirements Specification Techniques

A taxonomy is introduced and used as a backdrop against which current state-of-the-art in the requirements engineering field is reviewed. The emphasis is on identifying general trends and issues rather than offering the reader a literature survey. The contents of a requirements specification is presented in light of the consensus reached by both theoreticians and practitioners. The desirable proper ties of a requirements may alter the relative significance of difference properties. Finally, the classification of requirements specification techniques is approached from a total system design perspective. The paper shows that, despite significant growth, the requirements area still faces a number of important unresolved issues including the need for: broader formal foundation for both functional and non-functional requirements, greater degree of formality and automation, new requirements development methods, and higher level of integration in the overall design process

A Rigorous Approach to Building Formal System Requirements

This paper reports the author\u27s experience in the use of formal specifications and presents a step by step approach to developing functional requirements for computer-based systems. A simple model of system requirements is introduced first. A systematic approach to developing requirements by starting with the general model and adapting it to the needs to the problem at hand is described and illustrated by means of the simple but realistic example. A basic knowledge of predicate calculus and set theory is assumed on the part of the reader. The presentation is tutorial in nature

Technical Reviews: A Product Adoption Process

Technical reviews are an integral part of the software development process for any company concerned with software quality. This paper is neither a survey nor a comparative study of existing approaches but an attempt to reexamine the technical review process from a new perspective, the corporate culture. It is the contention of this paper that technically sound methods are effective only in a climate where (1) reviews are an integral part of the local culture and (2) there is no clear understanding of the kinds of technical and organizational needs the reviews are intended and able to satisfy. The paper puts forth the notion that, culturally, the reviews must serve as a vehicle for transforming the product of a single individual into a corporate product. The process of broadening both the authorship and the responsibility of the product from an individual to a team and, eventually, to a corporation is called product adoption

Functional Specification of Distributed Systems

A formal Distributed Systems Design Language (DSDL) is described. In DSDL, systems are described as nets of communicating processes. A net is defined by its processes, by the logical communications links between processes, and by the communications protocols. Each process in the net has its own local data, procedures that specify primitive operations over the data, and possesses the ability to exchange messages with other processes in the net. Some of these processes are used to model the system environment. The links identify the logical connections between processes. The way in which an individual link behaves in stipulated by the communication protocol associated with the link. DSDL is introduced by means of a highly simplified annotated example representative of the nature of the language

Total System Development Framework

Building on the fundamental assumption that effective methdologies are problem and environment dependent, a suggestion is made to distinguish between methodologies and the methodological frameworks they instantiate. TSD (Total System Development) is put forth as a candidate framework able to assist in the generation and evaluation of specific system development methodologies, where systems are defined as distributed hardware/software aggregates

Specifying Software/Hardware Interactions in Distributed Systems

This paper describes a system level specification approach that enables the designer to formulate and answer questions regarding the system\u27s logical correctness and performance characteristics when the interaction between the hardware and the software is important, i.e., when the impact of faults, failures, communication delay, hardware selection, scheduling policies, etc., must be considered. In the simplest terms, our concern extends beyond the traditional software correctness questions by addressing the issue of employing logical verification techniques to determine software correctness and performance characteristics when running on a particular distributed hardware architectures and using a particular operating system. A language called CSPS (an extension of Hoare\u27s CSP) is used in the illustration of the approach. Employing CSP as a base allows modelled systems to be verified using techniques already developed for verifying CSP programs

Formal Specifications of Geographic Data Processing Requirements

This paper establishes a formal foundation for the specification of Geographic Data Processing (GDP) requirements. The emphasis is placed on modeling data and knowledge requirements rather than processing needs. A subset of first order logic is proposed as the principal means for constructing formalizations of the GDP requirements in a manner that is independent of the data representation. Requirements executability is achieved by selecting a subset of logic compatible with the inference mechanisms available in Prolog. GDP significant concepts such as time, space and accuracy have been added to the formalization without losing Prolog implementabilty or separation of concerns. Rules of reasoning about time, space and accuracy (based on positional, temporal and fuzzy logic) may be compactly stated in a subset of second order predicate calculus and may be easily modified to meet the particular needs of specific application. Multiple views of the data and knowledge may coexist in the same formalization. The feasibility of the approach has been established with the aid of a tentative Prolog implementation of the formalism. The implementation also provides the means for graphical rendering of logical information on a high resolution color display

A Taxonomy of Current Issues in Requirements Engineering

The contents of a requirements specification is presented in light of the consensus reached both theoreticians and practitioners. The desirable properties of a requirements specification justified from a functionalist viewpoint and it is suggested that changes in the way one uses requirements may alter the relative significance of different properties. Finally, a classification requirements specification techniques is proposed and used as a backdrop against which current issues in the requirements engineering field are examined. The emphasis is on identifying general problem areas rather than offering the reader a literature survey. The paper shows that, despite significant growth, the requirements area still face a number of important unresolved issues including the need for: broader formal foundation for both functional and non-functional requirements, greater degree of formality and automation, new requirements development methods, and higher level of integration in the overall design process