SLAN-4?A Software Specification and Design Language

SLAN-4 (``Software Language-4') was developed to meet the need for a formal tool for specifying and designing large software systems. It provides language constructs for algebraic and axiomatic specifications and also pseudocode constructs for the design step. A major design goal was to ease subsequent refinements of a (given) specification. The design can start with a very informal specification, which can be implemented later using lower level concepts. This paper gives an overview of the SLAN-4 syntax and semantics. It concentrates on the most important aspects of: ? abstract data types, ? algebraic specification of abstract data types, and ? axiomatic specification of modules. Because the pseudocode part of SLAN-4 consists mainly of control structures similar to those in modern high-level programming languages, this element of the language is not separately described. The paper includes an example of how to use SLAN-4, and also the experiences gained in using the language to formally specify a real-world software product of about 18 000 lines of code written in an IBM internal high-level language.     

汇编语言在当今软件设计领域中能否生存

汇编语言是一门低级程序设计语言,它主要的功能是直接对硬件进行控制.虽然它是一门面向机器的语言,在可读性和移植性方面不及高级程序设计语言好,但用它所编写出来的程序能够在各种控制芯片上直接执行,具有效率高、反应快的特点,这是其它高级程序设计语言所无法超越的,所以汇编语言在当今软件设计领域中是无法被其它高级程序设计语言所替代的.     

An intermediate language to define dynamic semantics

An instruction set is given for an abstract machine which uses a pushdown stack as its principal memory. The proposed instructions serve the similar purposes of (1) defining the dynamic semantics of programming languages by describing the operations of programs on the abstract machine and (2) describing an intermediate language to be used in compiling programming languages into machine language. It is shown how the intermediate language can be used in the translation of the programming languages ADA, FORTRAN and PASCAL into IBM 360 assembly language and advantages over other intermediate languages such as three-address code and P-code.     

A supercomputer program development system

This paper describes a high-level programming system for constructing vector and array processor based software involving the parallel language Actus. The system functions on a cross-computer basis where a programmer develops Actus programs in a form that can be tested and transferred to the chosen supercomputer. The principles involved are, however, applicable to other similar block-structured high-level languages.     

The formal definition of semantics by string automata

An abstract machine called a string automaton (SA) is introduced in this paper. SAs are motivated by the need to formally define the semantics of programming languages in a manner accessible to the users of the language. The SA notation can be used to represent functions and computations in a clear, concise, graphical, and natural manner. After the class of SAs has been formally defined, it is shown how logic modules (resembling hardware circuit elements) and function modules (which define functions) can be expressed by SAs. Networks of SAs and their application to the construction of parsers is discussed. The definition of the language and hardware components of an interactive programming system by means of SAs is outlined.     

ZPL: a machine independent programming language for parallelcomputers

The goal of producing architecture-independent parallel programs is complicated by the competing need for high performance. The ZPL programming language achieves both goals by building upon an abstract parallel machine and by providing programming constructs that allow the programmer to “see” this underlying machine. This paper describes ZPL and provides a comprehensive evaluation of the language with respect to its goals of performance, portability, and programming convenience. In particular, we describe ZPt's machine-independent performance model, describe the programming benefits of ZPL's region-based constructs, summarize the compilation benefits of the language's high-level semantics, and summarize empirical evidence that ZPL has achieved both high performance and portability on diverse machines such as the IBM SP-2, Cray T3E, and SGI Power Challenge     

An environment for painless MIMD system development

An environment that lets system applications be expressed as virtual machines, through which architecture-independent multiple-instruction, multiple-data stream (MIMD) programs are written, is described. The virtual machine hides the hardware configuration from the programmer so that the MIMD programming environment always appears the same, regardless of the actual hardware. The data-definition and procedural high-level languages used in the environment and the generation of object code in the environment are discussed. The runtime configuration of the system and an implemented prototype of the system are described     

Towards the uniform implementation of declarative languages

Current implementation techniques for functional languages differ considerably from those for logic languages. This complicates the development of flexible and efficient abstract machines that can be used for the compilation of declarative languages combining concepts of functional and logic programming. We propose an abstract machine, called the JUMP-machine, which systematically integrates the operational concepts needed to implement the functional and logic programming paradigm. The use of a tagless representation for heap objects, which originates from the Spineless Tagless G-machine, supports the integration of different concepts. In this paper, we provide a functional logic kernel language and show how to translate it into the abstract machine language of the JUMP-machine. Furthermore, we define the operational semantics of the machine language formally and discuss the mapping of the abstract machine to concrete machine architectures. We tested the approach by writing a compiler for the functional logic language GTML. The obtained performance results indicate that the proposed method allows to implement functional logic languages efficiently.     

Hardware assisted high-level debugging

Hardware assistance has long been used for logic level and functional unit level hardware debugging, as well as for machine language level software debugging. Such hardware assistance includes probes to detect signals, comparators to identify matches with expected patterns, buffers to record selected events, and independent logic and software to analyze and interpret the observed events. It can also include the ability to generate selected signals to stimulate the object being debugged and the ability to isolate it from normal changes so its state can be examined. Through knowledge of the data structures and algorithms used by the operating systems, and the runtime representation, register usage, and code bursts produced by compilers, it is possible to take advantage of such hardware assistance in high-level debugging. High-level debugging here refers to debugging in terms of abstractions supported by the operating system and programming languages, as well as user defined abstractions built on top of these. This paper discusses design considerations behind a project to build such a hardware assisted high-level debugger.     

Polymorphic programming I. Another language designed on semantic principles

We wish to illustrate the potential of a thus far little explored avenue of programming language design–-namely the employment of types and routines as values in their own right within the framework of an Algol. In this first paper we pay particular attention to the development of highly orthogonal self-initializing data structures, and to the advantageous expressive power of polymorphism when combined with routine values so as to provide abstract data structures. The emphasis is on the design phase, rather than on the implementation details or precise syntactic structure of the envisaged language. A second, companion paper? discusses the design of a high-level orthogonal abstract architecture intended to support polymorphic languages in which routines are ‘first class’ values. The relationship of the abstract machine architecture to the programming language vis-a-vis the ‘semantic gap’ is then discussed from the viewpoint of compiling programs which are strongly typed while exploiting polymorphism. We feel that polymorphism is essential if truly general purpose programs, software tools, are to be written easily. The research reported herein is an effort towards realizing this goal.     

Executing continuation semantics: A comparison

Several authors have suggested translating denotational semantics into prototype interpreters written in high-level programming languages to provide evaluation tools for language designers. These implementations have generally been understandable when restricted to direct denotational semantics. This paper considers using two declarative programming languages, Prolog and Standard ML, to implement an interpreter that follows the continuation semantics of a small imperative programming language, called Gull. Each of the two declarative languages presents certain difficulties related to evaluation strategies and expressiveness. The implementations are compared in terms of their ease of use for prototyping, their resemblance to the denotational definitions, and their efficiency.     

Choosing a programming language

This paper evaluates the use of a functional language for implementing domain-specific functionality. The factors we consider when choosing a programming language are programmer productivity, maintainability, efficiency, portability, tool support, and software and hardware interfaces. The choice of programming language is a fine balancing act. Modern object-oriented languages such as Java and C# are more orthogonal and hide fewer surprises for the programmer, although the inevitable accumulation of features makes this statement less true with every new version of each language.     

LET模型的时间语义编程语言

嵌入式实时系统的正确性不仅取决于计算结果的正确性,更取决于产生结果时间的正确性.然而软件不确定的并发执行带来系统时间行为不可预测问题,使得验证复杂度升高,成本增加,为此实时系统领域提出了许多实时编程语言来提高系统的时间可预测性.LET(logical execution time)模型结合了同步模型ZET(zero e...     

Mixed language programming

Subroutines for numerical computation have in the past been written mainly in Fortran and in Algol 60, whereas most programming in the future is expected to be in more advanced languages, for example in Ada. It seems to be a great waste if it will become necessary to convert all existing numerical software into the new languages. What is needed is a facility to include subroutines written in the old languages into programs being written in the newer languages. In this paper an automatic procedure to facilitate the use of mixed languages is suggested, the purpose of the paper is to indicate the desirability for providing the required facilities, and to encourage discussion and further research in the area of mixed language programming.     

Knorc Calculus and Its Formal Semantics--To Honor my Friend Prof. Krieg-Brueckner''s 66th Birthday

This paper introduces the orchestration calculus Knorc, which is a conservative extension of the Orc calculus designed by J. Misra et. al. Orc is a simple but powerful calculus for wide area computing, whose simplicity makes it a solid kernel for orchestration programming. But on the other hand Orc leaves everything else to the programmer, which often makes the programming task complicated. The design idea of Knorc was to provide Orc with a delicately selected set of facilities to greatly increase the expressive power of the calculus and at the same time keep the calculus concise. The distinguished features of Knorc include, but not limited to: combination of process algebra and logic programming, site considered as remote Boolean procedure, Horn-like logic programming and inference, diversity of different parallelism mechanisms, network of abstract knowledge sources, open world assumption as opposed to closed world assumption where OWA means existing sites need not be known to the programmer, symmetric process-to-process communication, batch processing facilities of knowledge and data, as well as broad band message transmission. Besides introducing the general structures of the language Knorc, we present also a formal structural operational semantics. This is one of the major foci of this paper.     

Agent Programming in 3APL

An intriguing and relatively new metaphor in the programming community is that of an intelligent agent. The idea is to view programs as intelligent agents acting on our behalf. By using the metaphor of intelligent agents the programmer views programs as entities which have a mental state consisting of beliefs and goals. The computational behaviour of an agent is explained in terms of the decisions the agent makes on the basis of its mental state. It is assumed that this way of looking at programs may enhance the design and development of complex computational systems.To support this new style of programming, we propose the agent programming language 3APL. 3APL has a clear and formally defined semantics. The operational semantics of the language is defined by means of transition systems. 3APL is a combination of imperative and logic programming. From imperative programming the language inherits the full range of regular programming constructs, including recursive procedures, and a notion of state-based computation. States of agents, however, are belief or knowledge bases, which are different from the usual variable assignments of imperative programming. From logic programming, the language inherits the proof as computation model as a basic means of computation for querying the belief base of an agent. These features are well-understood and provide a solid basis for a structured agent programming language. Moreover, on top of that 3APL agents use so-called practical reasoning rules which extend the familiar recursive rules of imperative programming in several ways. Practical reasoning rules can be used to monitor and revise the goals of an agent, and provide an agent with reflective capabilities.Applying the metaphor of intelligent agents means taking a design stance. From this perspective, a program is taken as an entity with a mental state, which acts pro-actively and reactively, and has reflective capabilities. We illustrate how the metaphor of intelligent agents is supported by the programming language. We also discuss the design of control structures for rule-based agent languages. A control structure provides a solution to the problem of which goals and which rules an agent should select. We provide a concrete and intuitive ordering on the practical reasoning rules on which such a selection mechanism can be based. The ordering is based on the metaphor of intelligent agents. Furthermore, we provide a language with a formal semantics for programming control structures. The main idea is not to integrate this language into the agent language itself, but to provide the facilities for programming control structures at a meta level. The operational semantics is accordingly specified at the meta level, by means of a meta transition system.     

A concurrent abstract interpreter

Abstract interpretation [6] has been long regarded as a promising optimization and analysis technique for high-level languages. In this article, we describe an implementation of aconcurrent abstract interpreter. The interpreter evaluates programs written in an expressive parallel language that supports dynamic process creation, first-class locations, list data structures and higher-order procedures. Synchronization in the input language is mediated via first-class shared locations. The analysis computes intra- and inter-threadcontrol anddataflow information. The interpreter is implemented on top of Sting [12], a multi-threaded dialect of Scheme that serves as a high-level operating system for modern programming languages.