An abstract programming language and correctness proofs

The realization of an abstract programming language is a good approach for automating the software production process and facilitating the correctness proof of a software system.

This paper introduces a formal language for programming at the abstract level by combining Pascal with VDM (Vienna Development Method). The notation provided by the language obliges programmers to consider the correctness of programs throughout the whole process of programming, and the proof axiom and rules presented in this paper may be used to prove the correctness of programs. A complete example is given to illustrate how to program using APL and how to prove the correctness of programs using the given axiom and rules.     

A natural language discourse model to explain linear programming models and solutions

This paper presents a natural language (i.e., English) discourse model to explain a linear programming model and, possibly, its computed solution (which need not be optimal). Drawing from earlier syntactic translations, a semantic model is presented, based on economic input-output relations commonly found in large-scale linear programs. These are then shown how to form rule-driven explanations, which comprises a fundamental component of an intelligent mathematical programming system.     

A shorter proof that palindromes are not a Church-Rosser language, with extensions to almost-confluent and preperfect Thue systems

In 2002, Jurdziński and Lory? settled a long-standing conjecture that palindromes are not a Church-Rosser language. Their proof involved a difficult analysis of computation graphs associated with 2-pushdown-stack automata. We present a shorter and easier proof in terms of 1-tape Turing machines.We also discuss how the proof generalises to almost-confluent Thue systems and the differing powers of Church-Rosser, almost-confluent, and preperfect Thue systems in relation to palindromes.     

Pearl at the age of five: Case study of development and application of a common high order realtime programming language

The Programming language PEARL for industrial process automation has been developed since 1969. After extensive studies its final definition was frozen in 1976. Since then considerable experience has been gained with some 25 implementations and 200 applications.With PEARL at the age of three, these experiences are offered as a case study in this paper.The paper starts with a characterization of PEARL by indicating the requirements for such a tool, by classifying it with respect to other language types and by pleading for embedded realtime features. As PEARL has been submitted to ISO for international standardization, the question of how it meets the requirements set up by ISO is more thoroughly answered in Appendix A.The report of experience is given separately for implementation, application, and standardization with as much quantitative results as possible, including compiler behaviour, application areas, and economical benefit.For readers not yet familiar with PEARL a tutorial introduction by means of a simple but completely programmed control problem is given in Appendix B.