Denotational and operational semantics for prolog

The semantics of PROLOG programs is usually given in terms of the model theory of first-order logic. However, this does not adequately characterizethe computational behavior of PROLOG programs. PROLOG implementations typically use a sequential evaluation strategy based on the textual order of clauses and literals in a program, as well as nonlogical features like cut. In this work we develop a denotational semantics that captures thecomputational behavior of PROLOG. We present a semantics for “cut-free” PROLOG, which is then extended to PROLOG with cut. For each case we develop a congruence proof that relates the semantics to a standard operational interpreter. As an application of our denotational semantics, we show the correctness of some standard “folk” theorems regarding transformations on PROLOG programs.     

Complete high-performance cache system for the 80386

The 80386 is a high-performance third-generation microprocessor that is now standard in most top-of-the-range PCs. Like all similar processors operating at clock rates above 30 MHz, the 80386 must use cache memory if it is to operate efficiently. Without cache memory, the user must either pay a very high price for very fast RAM or employ slower memory by introducing wait states. This application note describes the 80386 bus interface and demonstrates how it can be interfaced to IDT cache tag RAMs to create a cache system. Although the report describes a relatively basic cache system, it covers all design considerations ranging from system timing to the programming of the PALs needed to implement the interface. A.C.     

Techniques of integrating Datalog with PROLOG

Since extending DATALOG to a general-purpose programming language seems very difficult,many projects have embedded a DATALOG-based query laguage into a procedural host language,such as CORAL,Glue-Nail,etc.Although DATALOG can be consideed as function-free PROLOG,they are very different in many aspects.For instance,DATALOG is declarative while PROLOG isn‘t,DATALOG takes “a-set-at-a-time” mode of evaluation but PROLOG takes “a-tuple-at-a-time”one,DATALOG is only a query language whereas PROLOG is a general-purpose programming language.It is thought that integrating DATALOG with PROLOG may take their advantages.KBASEP is such a language.It uses KBASE as the query language and PROLOG as its procedural host language,where KBASE is a ne extemsion of DATALOG with negation and function.This paper introduces the integration techniques used in KBASE-P system.     

The occur-check problem revisited

A method is presented for executing PROLOG programs which avoids almost all unnecessary occur-checks. The method is based on a dynamic classification of the context in which logical variables occur. No static global analysis of the PROLOG program is required to detect the places where an occur-check has to be made. The presented method has also an important side benefit. It considerably cuts down on the number of memory references during the execution of PROLOG programs. Furthermore, in most cases it avoids “trailing” and “untrailing” of unbound variables altogether. Due to this fact the employed method actually speeds up PROLOG execution. The method is discussed in terms of an actual implementation based on the Warren abstract PROLOG instruction set. However, the method should be applicable to other implementation models as well. No assumptions are made with respect to particular hardware.     

Implementing parallel algorithms in concurrent prolog: The Maxflow experience

This paper reports on the experience of implementing Shiloach and Vishkin's parallel Maxflow algorithm [7] in Concurrent PROLOG. The major difficulties in this endeavor were understanding the algorithm, which is intricate, and adapting it to the computational model of Concurrent PROLOG. In spite of the difficulties, we were able to produce a Concurrent PROLOG program that implements the algorithm and achieves the expected complexity bounds. The lack of destructive assignment in the logic program's computation model prevents PROLOG from being an efficient implementation language for many sequential algorithms. Our main conclusion is that, in concurrent algorithms, message passing is a powerful substitute for destructive assignment. It is therefore possible to write efficient Concurrent PROLOG implementations of concurrent algorithms.     

Login: a logic programming language with built-in inheritance

An elaboration of the PROLOG language is described in which the notion of first-order term is replaced by a more general one. This extended form of terms allows the integration of inheritance—an IS-A taxonomy—directly into the unification process rather than indirectly through the resolution-based inference mechanism of PROLOG. This results in more efficient computations and enhanced language expressiveness. The language thus obtained, called LOGIN, subsumes PROLOG, in the sense that conventional PROLOG programs are equally well executed by LOGIN.     

Negation as inconsistency. I

The notion of negation as inconsistency is motivated and introduced into PROLOG. This negation is fully compatible with classical negation and gives a version of PROLOG which is a stronger fragment of classical logic than ordinary PROLOG. It is intended that negation as inconsistency replace the notion of negation as failure. Negation as inconsistency can be generalized in a natural way and in its generalized form will include negation as failure as a special case.     

80386保护模式下的编程

详细讨论了 80 386 CPU的保护模式 ,该 32位的微处理器是 80 86的扩展 ,其运行速度更快 ,并且兼容以前的 CPU,80 386支持实模式和保护模式 ,在实模式下 80 386相当于一个可进行 32位处理的快速 80 86 ,只有在保护模式下 80 386才能发挥其全部强大的功能。 80 386还提供对虚拟内存和多任务的支持 ,并且设计了一个程序 ,实现在保护模式下的多任务运行     

PROLOG语言在计算机网络环境下的开发与应用

本文讨论了分布式计算机系统中进程通信的一种机制──远程过程调用（ＲＰＣ）的设计与实现。在此基础上，将ＲＰＣ机制扩充到ＰＲＯＬＯＧ语言中，使该语言具有网络通信能力，初步实现了计算机局域网络环境下ＰＲＯＬＯＧ语言的应用，为分布式专家系统的程序实用于网络探索新路。