nan Luqi

A prototyping language for real-time software

PSDL is a language for describing prototypes of real-time software systems. It is most useful for requirements analysis, feasibility studies, and the design of large embedded systems. PSDL has facilities for recording and enforcing timing constraints, and for modeling the control aspects of real-time systems using nonprocedural control constraints, operator abstractions, and data abstractions. The language has been designed for use with an associated prototyping methodology. PSDL prototypes are executable if supported by a software base containing reusable software components in an underlying programming language (e.g. Ada). >

Software evolution through rapid prototyping

Rapid prototyping is defined, and its role in software evolution is examined. Software evolution refers to all activities that change a software system. It differs from maintenance in that the latter is done after the initial development, whereas evolution activities are interleaved with the initial development and continue after the delivery of the initial version of the system. In the authors approach to rapid prototyping, software systems are delivered incrementally and requirements analysis continues throughout the process, interleaved with implementation and evolution. The focus is on reducing requirements errors through prototyping before undertaking the incremental implementation effort for each deliverable version of the system. The evolution of a hyperthermia system is considered as an example.<<ETX>>

Formal methods: promises and problems

Successfully applying formal methods to software development promises to move us closer to a true engineering discipline. The authors offer suggestions for overcoming the problems that have hindered the use of formal methods thus far.

A computer-aided prototyping system

A description is given of an approach to rapid prototyping that uses a specification language (the Prototype-System Description Language, PSDL) integrated with a set of software tools. including an execution support system, a rewrite system, a syntax-directed editor with graphics capabilities, a software base, a design database, and a design-management system. The prototyping language lets the designer use dataflow diagrams with nonprocedural control constraints as part of the specification of a hierarchically structured prototype. The resulting description is free from programming-level details, in contrast to prototypes constructed with a programming language. The discussion covers the language and method, rewrite subsystem, design manager, software base, and execution support.<<ETX>>

A graph model for software evolution

A graph model of software evolution is presented. The author seeks to formalize the objects and activities involved in software evolution in sufficient detail to enable automatic assistance for maintaining the consistency and integrity of an evolving software system. This includes automated support for propagating the consequences of a change to a software system. The evolution of large and complex software systems receives particular attention. >

Rapidly prototyping real-time systems

A prototyping approach that uses modularity and reusable components is described that enables large real-time systems to be prototyped rapidly. It combines a computational model tailored for real-time systems with a high-level prototyping language (the Prototype System Description Language), a systematic design method for rapid prototype construction, and an automated prototyping environment. The method meets the following requirements: the prototype satisfies its requirements and is traceable to them; the prototype is easy to modify; and the prototype code is easy to read and analyze.<<ETX>>

An introduction to rapid system prototyping

The implementation and maintenance of industrial applications have continuously become more and more difficult. In this context, one problem is the evaluation of complex systems. The IEEE defines prototyping as a development approach promoting the implementation of a pilot version of the intended product. This approach is a potential solution to the early evaluation of a system. It can also be used to avoid the shift between the description/specification of a system and its implementation. This brief introduction to the special section on rapid system prototyping illustrates a current picture of prototyping.

A survey of software reuse repositories

Reuse libraries are organizations of personnel, procedures, tools, and software components directed toward facilitating software component reuse to meet specific cost-effectiveness and productivity goals. The paper gives a survey of the major software reusable component repositories. This survey will be a base to develop future efficiently searchable, user-friendly, useful, and well-organized repositories.

Using transformations in specification-based prototyping

The authors explore the use of software transformations for software evolution. Meaning-preserving program transformations have been widely used for program development from a fixed initial specification. They consider a wider class of transformations to support development in which the specification evolves, rather than being fixed in advance. A new and general classification of transformations based on their effect on system interfaces, externally observable behavior, and abstraction level of a system description is presented. This classification is used to rearrange chronological derivation sequences containing meaning-changing transformations into lattices containing only meaning-preserving transformations. A process model for software evolution that utilizes prototyping techniques is described. Ways in which this class of transformations can be used to support such a process are considered. A set of examples are presented to illustrate the ideas. Software tool support and directions for future research are discussed. >

Compositional semantics of a real-time prototyping language

The formal semantics of a prototyping language for hard real-time systems, PSDL, is given. PSDL provides a data flow notation augmented by application-orientation timing and control constraints to describe a system as a hierarchy of networks of processing units communicating via data streams. The semantics of PSDL are defined in terms of algebraic high-level Petri nets. This formalism combines algebraic specifications of abstract data types with process and concurrency concepts of Petri nets. Its data abstraction facilities are used to define the meaning of PSDL data types, while high-level Petri nets serve to model the casual and timing behavior of a system. The net model exposes potential concurrency of computation and makes all synchronization needs implied by timing and control constraints explicit and precise. Time is treated as state of clocks, and clocks are modeled as ordinary system components. The net semantics provides the basis for applying analysis techniques and semantic tools available for high-level Petri nets. >