A Formal Semantics for DAI Language NUML

Traditional AI systems are brittle in the sense that they fail miserably when presented with problems even sliphtly outside of their limited range of expertise.A powerful,extensible strategy of Distributed Artificial Intelligence (DAI) for overcoming such bounds is to put the system in a society of systems.So the ability to coordinate group activities of individuals and to communicate between each other is necessary for a language describing DAI systems.Agent-oriented language NUML is such a language.It is a specific kind of object-oriented language.To give formal semantics to NUML,there is the problem to formalise object-oriented programming paradigm which is still open.The theory of higher-order π-calculus is a concurrent computation model with sufficient capability,which provides us a mathematical tool to do the formalization.This paper tries to use higher-order π-calculus to formalise NUML.     

知识推理描述语言NUML的设计,实现及应用

知识推理描述语言ＮＵＭＬ用于描述多智能实体系统中协调地问题求解过程，它是一种具有良好数学基础的多风范语言，以智能代理为其基本程序结构，提供元级推理的描述能力。     

NUMLS中的多态类型检测

本文从ＮＵＭＬ函数式部分实现中遇到的类型检测问题着手，讨论类型检测问题到半合一问题的转化，给出半合一的转换式求解机制和该转换规则集的可靠性和完备性定理。     

Implementing tactics and tacticals in a higher-order logic programming language

We argue that a logic programming language with a higher-order intuitionistic logic as its foundation can be used both to naturally specify and implement tactic-style theorem provers. The language extends traditional logic programming languages by replacing first-order terms with simply-typed -terms, replacing first-order unification with higher-order unification, and allowing implication and universal quantification in queries and the bodies of clauses. Inference rules for a variety of inference systems can be naturally specified in this language. The higher-order features of the language contribute to a concise specification of provisos concerning variable occurrences in formulas and the discharge of assumptions present in many inference systems. Tactics and tacticals, which provide a framework for high-level control over search for proofs, can be directly and naturally implemented in the extended language. This framework serves as a starting point for implementing theorem provers and proof systems that can integrate many diversified operations on formulas and proofs for a variety of logics. We present an extensive set of examples that have been implemented in the higher-order logic programming language Prolog.     

面向大规模语料的语言模型研究新进展

N元语言模型是统计机器翻译、信息检索、语音识别等很多自然语言处理研究领域的重要工具.由于扩大训练语料规模和增加元数对于提高系统性能很有帮助,随着可用语料迅速增加,面向大规模训练语料的高元语言模型(如N≥5)的训练和使用成为新的研究热点.介绍了当前这个问题的最新研究进展,包括了集成数据分治、压缩和内存映射的一体化方法,基于随机存取模型的表示方法,以及基于分布式并行体系的语言模型训练与查询方法等几种代表性的方法,展示了它们在统计机器翻译中的性能,并比较了这些方法的优缺点.     

A new representation of systems with frictional unilateral constraints and its Baumgarte-like relaxation

This paper proposes a new representation of multibody mechanical systems involving three-dimensional frictional unilateral constraints. The new representation is of the form of a differential algebraic inclusion (DAI) employing a normal cone with a non-Euclidean, singular norm metric. It can be seen as a generalization of a differential algebraic equation (DAE) using Lagrange multipliers, which has been used to represent mechanical systems with equality constraints. The paper also presents an approach to approximate the aforementioned DAI by another form of DAI, which can be equivalently converted into an ordinary differential equation (ODE). The approach can be seen as a generalization of the Baumgarte stabilization, which was originally developed for DAEs. The new DAI representation and its ODE approximation are illustrated with some simple examples.     

Typing termination in a higher-order concurrent imperative language

We propose means to predict termination in a higher-order imperative and concurrent language à la ML. We follow and adapt the classical method for proving termination in typed formalisms, namely the realizability technique. There is a specific difficulty with higher-order state, which is that one cannot define a realizability interpretation simply by induction on types, because applying a function may have side-effects at types not smaller than the type of the function. Moreover, such higher-order side-effects may give rise to computations that diverge without resorting to explicit recursion. We overcome these difficulties by introducing a type and effect system for our language that enforces a stratification of the memory. The stratification prevents the circularities in the memory that may cause divergence, and allows us to define a realizability interpretation of the types and effects, which we then use to establish that typable sequential programs in our system are guaranteed to terminate, unless they use explicit recursion in a divergent way. We actually prove a more general fairness property, that is, any typable thread yields the scheduler after some finite computation. Our realizability interpretation also copes with dynamic thread creation.     

Hybrid

Combining higher-order abstract syntax and (co)-induction in a logical framework is well known to be problematic. We describe the theory and the practice of a tool called Hybrid, within Isabelle/HOL and Coq, which aims to address many of these difficulties. It allows object logics to be represented using higher-order abstract syntax, and reasoned about using tactical theorem proving and principles of (co)induction. Moreover, it is definitional, which guarantees consistency within a classical type theory. The idea is to have a de Bruijn representation of λ-terms providing a definitional layer that allows the user to represent object languages using higher-order abstract syntax, while offering tools for reasoning about them at the higher level. In this paper we describe how to use Hybrid in a multi-level reasoning fashion, similar in spirit to other systems such as Twelf and Abella. By explicitly referencing provability in a middle layer called a specification logic, we solve the problem of reasoning by (co)induction in the presence of non-stratifiable hypothetical judgments, which allow very elegant and succinct specifications of object logic inference rules. We first demonstrate the method on a simple example, formally proving type soundness (subject reduction) for a fragment of a pure functional language, using a minimal intuitionistic logic as the specification logic. We then prove an analogous result for a continuation-machine presentation of the operational semantics of the same language, encoded this time in an ordered linear logic that serves as the specification layer. This example demonstrates the ease with which we can incorporate new specification logics, and also illustrates a significantly more complex object logic whose encoding is elegantly expressed using features of the new specification logic.     

基于高阶逻辑的复杂结构归纳学习研究

归纳学习的目的在于发现样例与离散的类之间的映射关系,样例及归纳的映射都需用某个形式化语言描述.归纳学习器采用的形式化语言经历了属性-值语言、一阶逻辑、类型化的高阶逻辑三个阶段,后者能克服前二者在知识表达及学习过程中的很多缺点.本文首先阐述了基于高阶逻辑的复杂结构归纳学习产生的历史背景;其次介绍了基于高阶逻辑的编程语言--Escher的知识描述形式及目前已提出的三种学习方法;复杂结构的归纳学习在机器学习领域的应用及如何解决一些现实问题的讨论随后给出; 最后分析了复杂结构归纳学习的研究所面临的挑战性问题.     

Program equivalence in a simple language with state

We examine different approaches to reasoning about program equivalence in a higher-order language which incorporates a basic notion of state: references of unit type (names). In particular, we present three such methods stemming from logical relations, bisimulation techniques and game semantics respectively. The methods are tested against a surprisingly difficult example equivalence at second order which exploits the intricacies of the language with respect to privacy and flow of names, and the ensuing notion of local state.     

Communication infrastructure in distributed scheduling

The emergence of distributed artificial intelligent (DAI) introduced a new approach to solve scheduling problems by a set of scheduling systems that interact with each other in the problem-solving process. In this paper, we describe a communication infrastructure to handle connection and communication between distributed Internet scheduling systems for distributed applications. First, we present an agent model of distributed scheduling systems where agents can communicate and coordinate activities with each other via an agent communication language. Then, we define the syntax and semantics for the agent communication languages, and negotiation mechanism. Following that, we discuss the design and development of the prototype for the multi-agent scheduling systems. We conclude with a discussion of communication issues for heterogeneous agent-based scheduling systems to solve distributed scheduling problems.     

On Migrating Threads

Based on the notion of persistent threads in Tycoon (Matthes and Schmidt, 1994), we investigate thread migration as a programming construct for building activity-oriented distributed applications. We first show how a straight-forward extension of a higher-order persistent language can be used to define activities that span multiple (semi-) autonomous nodes in heterogeneous networks. In particular, we discuss the intricate binding issues that arise in systems where threads are first-class language citizens that may access local and remote, mobile and immobile resources.We also describe how our system model can be understood as a promising generalization of the more static architecture of first-order and higher-order distributed object systems. Finally, we give some insight into the implementation of persistent and migrating threads and we explain how to represent bindings to ubiquitous resources present at each node visited by a migrating thread on the network to avoid excessive communication or storage costs.     

Secure Information Flow via Linear Continuations

Security-typed languages enforce secrecy or integrity policies by type-checking. This paper investigates continuation-passing style (CPS) as a means of proving that such languages enforce noninterference and as a first step towards understanding their compilation. We present a low-level, secure calculus with higher-order, imperative features and linear continuations.Linear continuations impose a stack discipline on the control flow of programs. This additional structure in the type system lets us establish a strong information-flow security property called noninterference. We prove that our CPS target language enjoys the noninterference property and we show how to translate secure high-level programs to this low-level language. This noninterference proof is the first of its kind for a language with higher-order functions and state.     

Monolithic and modular termination analyses for higher-order attribute grammars

In this paper we describe a sound, but not complete, analysis to prove the termination of higher-order attribute grammar evaluation caused by the creation of an unbounded number of (finite) trees as local tree-valued attributes, which are then themselves decorated with attributes. The analysis extracts a set of term-rewriting rules from the grammar that model creation of new syntax trees during the evaluation of higher-order attributes. If this term rewriting system terminates, then only a finite number of trees will be created during attribute grammar evaluation. The analysis places an ordering on nonterminals to handle the cases in which higher-order inherited attributes are used to ensure that a finite number of trees are created using such attributes. When paired with the traditional completeness and circularity analyses for attribute grammars and the assumption that each attribute equation defines a terminating computation, this analysis can be used to show that attribute grammar evaluation will terminate normally. This analysis can be applied to a wide range of common attribute grammar idioms and has been used to show that evaluation of our specification of Java 1.4 terminates. We also describe a modular version of the analysis that is performed on independently developed language extension grammars and the host language being extended. If the extensions individually pass the modular analysis then their composition is also guaranteed to terminate.     

一种结合MDA的高阶模型转换方法

模型转换是MDA的关键技术,也是MDA的研究热点。目前,不同的MDA开发平台都有一套相对独立的开发技术和转换框架,这使平台之间缺乏兼容性,模型转换代码重用困难。究其原因是缺少一种与具体转换语言相对应,且与平台无关的转换规则模型。为了解决以上问题,将高阶模型转换的思想与模型驱动软件开发相结合,提出了一种构造模型转换规则的高阶转换元模型,并以ATL语言为例展示了高阶转换元模型的使用方法;最后通过一个实例验证了该方法的可行性和可用性。该方法提高了模型转换语言的抽象层次,降低了模型转换语言的重用难度,在一定程度上解决了模型转换技术不兼容的问题。     

Zero—a blend of static typing and dynamic metaprogramming

Zero is an experimental statically typed, fully object-oriented reflective programming language. Reflective features cover introspection as well as structural and behavioural reflection. The reflective facilities include safe method and class replacements and detailed modification of methods. These enable Zero programs to quickly accommodate to run-time requirements. Behavioural reflection is realised using handlers (hooks), which may be attached to all language constructs based on closures. Zero provides an efficient static typing system with run-time extensions. Methods are first class values and are represented as objects when such representation is required. By using such representation, Zero provides elegant use of statically typed higher-order methods.     

Distributed artificial intelligence from a socio-cognitive standpoint: Looking at reasons for interaction

Distributed Artificial Intelligence (DAI) deals with computational systems where several intelligent components interact in a common environment. This paper is aimed at pointing out and fostering the exchange between DAI and cognitive and social science in order to deal with the issues of interaction, and in particular with the reasons and possible strategies for social behaviour in multi-agent interaction is also described which is motivated by requirements of cognitive plausibility and grounded the notions of power, dependence and help. Connections with human-computer interaction are also suggested.     

A Higher-Order Calculus for Graph Transformation

This paper presents a formalism for defining higher-order systems based on the notion of graph transformation (by rewriting or interaction). The syntax is inspired by the Combinatory Reduction Systems of Klop. The rewrite rules can be used to define first-order systems, such as graph or term-graph rewriting systems, Lafont's interaction nets, the interaction systems of Asperti and Laneve, the non-deterministic nets of Alexiev, or a process calculus. They can also be used to specify higher-order systems such as hierarchical graphs and proof nets of Linear Logic, or to specify the operational semantics of graph-based languages.     

An architectural framework for CKBS applications

This paper presents an architectural framework for cooperating knowledge based systems (CKBSs) with parallels drawn from the multiagent systems of DAI. A CKBS is distinguished from a multiagent system by its need to provide a workable approach for real-world distributed applications. The framework proposed considers only interagent activities in what is called transaction-oriented processing. The framework, based largely on well-tested computer science concepts, provides for a multilayered edifice with information transparency, and a multilevel schema to suit different user expertise. It permits dynamic definition of cooperation strategies for different tasks as required, in a high-level language providing relative ease of use. A particular novelty is the interpretation of actions as side-effects of update operations on action tuples transmitted among agents via what are called shadows. This provides the generality needed. Effectiveness, flexibility, and ease of use are some of the key considerations