2APL: a practical agent programming language

This article presents a BDI-based agent-oriented programming language, called 2APL (A Practical Agent Programming Language). This programming language facilitates the implementation of multi-agent systems consisting of individual agents that may share and access external environments. It realizes an effective integration of declarative and imperative style programming by introducing and integrating declarative beliefs and goals with events and plans. It also provides practical programming constructs to allow the generation, repair, and (different modes of) execution of plans based on beliefs, goals, and events. The formal syntax and semantics of the programming language are given and its relation with existing BDI-based agent-oriented programming languages is discussed.     

Dynamics of symbol systems

To implement diverse and partial flow of information in cognitive processes, we need a design method without explicit stipulation of domain/task-dependent information flow, together with a control scheme for guiding information processing to concern only important information depending on contexts. A computational architecture is proposed which is based on a first-order logic program with a dynamics. The declarative semantics of the logic program is defined by measuring the degree of violation in terms ofpotential energy, and a control scheme for both analog and symbol computation is derived from the resultant dynamics, which replaces domain/task-dependent procedures, hence avoiding intractable complexity in the system design. This inherent integration of the control scheme with the declarative semantics guarantees that inferences are naturally centered around relevant information in a context sensitive manner. The essence of inference mechanisms proposed so far, such as weighted abduction and marker passing, are also subsumed by this dynamical control. All this justifies further exploration for improving this sort of formalism to deal with large, real-world problems.     

Heuristic knowledge representation of production scheduling: An integrated modeling approach

In spite of the efforts to automate production scheduling systems, most manufacturing plants rely on human schedulers for their practical production scheduling due mainly to the complexity and unpredictability of the manufacturing systems. One of the reasons for the difficulties in automating the production scheduling process is the lack of an explicit representation scheme of heuristic scheduling knowledge.

In this paper, an integrated modeling approach is presented to represent the complicated heuristic knowledge in production scheduling systems. The integrated modeling approach is based on object-oriented and event-driven modeling. It provides the explicit, declarative and executable representation of heuristic scheduling knowledge which aids the communication between human schedulers and system analysts. The declarative and executable representation of scheduling knowledge will enhance the flexibility of production scheduling systems and aid the development of production scheduling information systems.

A heuristic production scheduling model of a tire manufacturing system is used throughout the paper to illustrate the concepts and applicability of the approach.     

Clausal Logic and Logic Programming in Algebraic Domains

We introduce a domain-theoretic foundation for disjunctive logic programming. This foundation is built on clausal logic, a representation of the Smyth powerdomain of any coherent algebraic dcpo. We establish the completeness of a resolution rule for inference in such a clausal logic; we introduce a natural declarative semantics and a fixed-point semantics for disjunctive logic programs, and prove their equivalence; finally, we apply our results to give both a syntax and semantics for default logic in any coherent algebraic dcpo.     

描述逻辑εL循环术语集的混合推理

循环术语集是描述逻辑长期以来的研究难点, 它最基本的问题即语义及推理问题没有得到合理的解决. 分析了描述逻辑循环术语集的研究现状和存在的问题, 在Baader和Brandt的基础上进一步研究了描述逻辑εL循环术语集的混合推理问题. 给出了εL的混合循环知识库的语法和语义(包括不动点语义和描述语义). 针对εL循环术语集混合推理的需要, 提出了TBox-完全的概念, 并重新定义了描述图(包括语法描述图和语义描述图).使用描述图之间的模拟关系和TBox-完全概念给出了最大不动点语义和描述语义下εL混合循环知识库的实例检测推理算法, 证明了推理算法的正确性, 并给出了推理算法的复杂性定理.     

Engineering formal requirements: An analysis and testing method for Z documents

Z is a declarative, non‐executable specification language; its diffusion in the field of requirements engineering outside academia is slow but growing. In this paper we focus on some methods for analyzing and testing Z specification documents, with special emphasis on non‐sequential systems specifications. We describe two techniques we have adopted: the former allows the specifier to add to the requirements document a number of properties that then can be checked using a formal semantics; the latter makes it possible to build directly from the requirements specification document a distributed prototype which can be executed and tested over a network of workstations.     

New approach to requirements trade-off analysis for complex systems

We propose a faceted requirement classification scheme for analyzing heterogeneous requirements. The representation of vague requirements is based on L.A. Zadeh's (1986) canonical form in test score semantics and an extension of the notion of soft conditions. The trade-off among vague requirements is analyzed by identifying the relationship between requirements, which could be either conflicting, irrelevant, cooperative, counterbalance, or independent. Parameterized aggregation operators, fuzzy and/or, are selected to combine individual requirements. An extended hierarchical aggregation structure is proposed to establish a four-level requirements hierarchy to facilitate requirements and criticalities aggregation through the fuzzy and/or. A compromise overall requirement can be obtained through the aggregation of individual requirements based on the requirements hierarchy. The proposed approach provides a framework for formally analyzing and modeling conflicts between requirements, and for users to better understand relationships among their requirements     

Hybrid knowledge bases

Deductive databases that interact with, and are accessed by, reasoning agents in the real world (such as logic controllers in automated manufacturing, weapons guidance systems, aircraft landing systems, land-vehicle maneuvering systems, and air-traffic control systems) must have the ability to deal with multiple modes of reasoning. Specifically, the types of reasoning we are concerned with include, among others, reasoning about time, reasoning about quantitative relationships that may be expressed in the form of differential equations or optimization problems, and reasoning about numeric modes of uncertainty about the domain which the database seeks to describe. Such databases may need to handle diverse forms of data structures, and frequently they may require use of the assumption-based nonmonotonic representation of knowledge. A hybrid knowledge base is a theoretical framework capturing all the above modes of reasoning. The theory tightly unifies the constraint logic programming scheme of Jaffar and Lassez (1987), the generalized annotated logic programming theory of Kifer and Subrahmanian (1989), and the stable model semantics of Gelfond and Lifschitz (1988). New techniques are introduced which extend both the work on annotated logic programming and the stable model semantics     

A rule based knowledge transaction model for mobile environments

In this paper, we propose and formalize a rule based knowledge transaction model for mobile environments. Our model integrates the features of both mobile environments and intelligent agents. We use logic programming as a mathematic tool and formal specification method to study knowledge transaction in mobile environments. Our knowledge transaction model has the following major advantages: (1) It can be used for knowledge transaction representation, formalization and knowledge reasoning in mobile environments. (2) It is knowledge oriented and has a declarative semantics inherited from logic programming. (3) It is a formalization that can be applied to general problem domains. We show that our model can be used for knowledge transaction representation, formalization and knowledge reasoning in mobile environments.     

On the declarative and procedural semantics of deductive object-oriented systems

We present declarative and procedural semantics for a deductive object-oriented language, Gulog. The declarative semantics is based on preferred minimal models. We describe both bottom-up and top-down query evaluation procedures and show that they are sound with respect to the declarative semantics. The results contribute to our understanding of the interaction of inheritance, overriding and deduction in the presence of both functional and set-valued methods, and multiple inheritance.     

Specification by-example of virtual agents behavior

The development of virtual agents running within graphic environments which emulate real-life contexts may largely benefit from the use of visual specification by-example. To support this specification, the development system must be able to interpret the examples and cast their underlying rules into an internal representation language. This language must find a suitable trade-off among a number of contrasting requirements regarding expressiveness, automatic executability, and suitability to the automatic representation of rules deriving from the analysis of examples. A language is presented which attains this trade-off by combining together an operational and a declarative fragment to separately represent the autonomous execution of each individual agent and its interaction with the environment, respectively. While the declarative part permits to capture interaction rules emerging from specification examples, the operational part supports the automatic execution in the operation of the virtual environment. A system is presented which embeds this language within a visual shell to support a behavioral training in which the animation rules of virtual agents are defined through visual examples     

约束程序设计语言COPS的设计与实现

约束程序设计作为面向智能应用的实用型程序设计风格正在AI领域产生越来越大的影响，其关键问题是如何将说明性的知识表示、系统化和启发式的推理搜索能力以及合理的确定性计算开销统一起来。该文介绍了设计实现的并发约束程序设计语言COPS。COPS系统的主要目标是探索智能语言的实用化与工程化，使其能够真正解决现实世界中用常规语言难以实现的智能应用问题。还介绍了COPS语言的表示及涉及的主要推理技术。     

模糊描述逻辑L-ALCN

为了使描述逻辑能够处理更一般化的模糊信息,Straccia给出了基于完备格的L-ALC描述逻辑系统.在该方法的基础上,提出了带数量约束算子的L-ALCN系统,给出了L-ALCN的语法,并详细给出了概念(≥n R)和(≤n R)的语义.经典的描述逻辑系统中引入了数量约束算子后,角色R就出现了多个后继.当系统的真子集扩充到完备格时,角色R的后继和断言的真值同时出现了多个.为了保证推理算法的合理性且得到可行的计算复杂度,引入了一个特殊的集合D\\-L(c),并且利用集合D\\-L(c)扩展了完备格上的两条运算性质.在这些工作的基础上,深入研究了系统的推理算法,并证明了算法的终止性、可靠性与完全性.相对于L-ALC,系统L-ALCN具有更强的表达能力,并且L-ALCN的计算复杂度是Pspace完全的.     

带传递关系和存在量词的描述逻辑MSC推理

分析了描述逻辑非标准推理的重要性,特别分析了描述逻辑MSC推理的研究现状和存在的问题.针对目前描述逻辑MSC推理不能同时处理传递关系和存在量词的不足,研究了带传递关系和存在量词的描述逻辑εL+的MSC推理问题.提出了一种新的εL+-述图,利用描述树和描述图给出了描述逻辑εL+的MSC近似推理算法,并利用εL+-描述树同态和εL+-描述树描述图同态证明了MSC近似推理算法的正确性.作为一个附带的结果,利用εL+-描述树描述图同态给出了εL+的实例推理算法,也证明了实例推理算法的正确性.     

Production systems with negation as failure

We study action rule-based systems with two forms of negation, namely classical negation and "negation as failure to find a course of action". We show, by means of several examples, that adding negation as failure to such systems increases their expressiveness in the sense that real-life problems can be represented in a natural and simple way. Then we address the problem of providing a formal declarative semantics to these extended systems by adopting an argumentation-based approach which has been shown to be a simple unifying framework for understanding the declarative semantics of various nonmonotonic formalisms. In this way, we naturally define the grounded (well-founded), stable and preferred semantics for production systems with negation as failure. Next, we characterize the class of stratified production systems, which enjoy the properties that the above-mentioned semantics coincide and that negation as failure to find a course of action can be computed by a simple bottom-up operator. Stratified production systems can be implemented on top of conventional production systems in two ways. The first way corresponds to the understanding of stratification as a form of priority assignment between rules. We show that this implementation, though sound, is not complete in the general case. Hence, we propose a second implementation by means of an algorithm which transforms a finite stratified production system into a classical one. This is a sound and complete implementation, though it is computationally hard     

带n-元存在量词的描述逻辑MSC推理

分析了描述逻辑非标准推理的重要性,特别分析了描述逻辑MSC(Most Specific Concept)推理的研究现状和存在的问题.针对目前描述逻辑MSC推理不能处理n-元存在量词的不足,研究了带n-元存在量词的描述逻辑εL(n)的MSC推理问题.提出了一种新的εL(n)一描述图,利用描述树和描述图给出了描述逻辑εL(n)的MSC近似推理算法,并利用εL(n)-描述树嵌套和εL(n)-描述树描述图同态证明了MSC近似推理算法的正确性.作为一个附带的结果,利用εL(n)-描述树描述图同态给出了εL(n)-的实例推理算法,也证明了实例推理算法的正确性.     

Transactions and updates in deductive databases

In this paper, we develop a new approach that provides a smooth integration of extensional updates and declarative query languages for deductive databases. The approach is based on a declarative specification of updates in rule bodies. Updates are not executed as soon as evaluated. Instead, they are collected and then applied to the database when the query evaluation is completed. We call this approach nonimmediate update semantics. We provide a top-down and equivalent bottom-up semantics which reflect the corresponding computation models. We also package set of updates into transactions and we provide a formal semantics for transactions. Then, in order to handle complex transactions, we extend the transaction language with control constructors still preserving formal semantics and semantics equivalence