The Complexity of Modellability in Finite and Computable Signatures of a Constraint Logic for Head-Driven Phrase Structure Grammar

The SRL (speciate re-entrant logic) of King (1989) is a sound, complete and decidable logic designed specifically to support formalisms for the HPSG (head-driven phrase structure grammar) of Pollard and Sag (1994). The SRL notion of modellability in a signature is particularly important for HPSG, and the present paper modifies an elegant method due to Blackburn and Spaan (1993) in order to prove that

衰落网络信道通信能力建模仿真分析

对衰落网络信道通信能力进行分析,对网络遇到攻击后使信道衰落的修复具有重要的意义.网络入侵对信道产生的衰落性方面具有随机性和不可控性,不同网络受到不同入侵破坏后,网络信道的衰落程度也不同,引起的网络通信能力下降程度也不同.传统的方法仅仅以相同损伤权值认定入侵破坏衰落过程,对信道衰落程度与入侵强度间接的关联性分析较为模糊,存在一定的弊端.提出一种依据网络信息熵的衰落网络信道通信能力评估模型,从计算机网络受到弱入侵和强入侵后信道衰落程度的角度,分析了网络熵的概念,依据简化的网络信道性能指标规范,采用网络熵差的运算方法,将层次分析法应用于衰落网络信道通信能力的建模中,基于衰落网络信道通信能力评估层次结构模型,塑造评估矩阵,实现衰落网络信道通信能力的准确分析.实验结果说明,模型在网络通信效率、网络信道利用率以及信道延迟率三方面都优于传统模型,模型能够准确分析衰落网络信道通信能力.     

一种基于能力的轻量级SIP安全机制研究

本文先简要概述了SIP应用背景和重要概念,然后详细分析了SIP面临的安全威胁以及现有安全解决方案,主要为安全认证和加密,讨论了几种典型方案的原理和不足.随后仔细研究了一种先进的基于共享用户密码进行密钥协商的轻量级的SIP安全认证、加密机制,并加入一次口令机制加以改进.随后借鉴了一种基于能力的IP-DOS控制思想,结合S...     

Formalisations and applications of BPMN

We present two formalisations of the Business Process Modelling Notation (BPMN). In particular, we introduce a semantic model for BPMN in the process algebra CSP; we then study an augmentation of this model in which we introduce relative timing information, allowing one to specify timing constraints on concurrent activities. By exploiting CSP refinement, we are able to show some relationships between the timed and the untimed models. We then describe a novel empirical studies’ model, and the transformation to BPMN, allowing one to apply our formal semantics for analysing different kinds of workflows. To provide a better facility for describing behaviour specification about a BPMN diagram, we also present a pattern-based approach using which a workflow designer could specify properties which could otherwise be difficult to express. Our approach is specifically designed to allow behavioural properties of BPMN diagrams to be mechanically verified via automatic model checking as provided by the FDR tool. We use two examples to illustrate our approach.     

浅谈职业院校IT类教师的素质与能力

随着信息时代的到来,对职业院校IT类教师的素质与能力提出了新的要求。教师应具有先进的教育理念,高尚的品德修养,合理的知识结构和较强的业务能力,这样才能适应职业教育的发展需要,才能为社会培养合格的实用型人才。     

LINEAR ITERATED PUSHDOWNS

This paper discusses variants of nondeterministic one-way S -automata and context-free S -grammars where S is a storage type. The framework that these systems provide can be used to give alternative formulations of embedded pushdown automata and linear indexed grammars. The embedded pushdown automata is obtained by means of a linear version of a class of storage types called iterated pushdowns. Linear indexed grammar is obtained by using the pushdown storage type and restricting the way in which the grammar uses its storage.     

Decentralized Navigation Functions for Multiple Robotic Agents with Limited Sensing Capabilities

The decentralized navigation function methodology, established in our previous work for navigation of multiple holonomic agents with global sensing capabilities is extended to the case of local sensing capabilities. Each agent plans its actions without knowing the destinations of the others and the positions of those agents lying outside its sensing neighborhood. The stability properties of the closed loop system are checked via Lyapunov stability techniques for nonsmooth systems. The collision avoidance and global convergence properties are verified through simulations. This work was partially presented in [5].     

相位校正器补偿能力的频域特性仿真分析

在自适应光学系统仿真分析中,通常用变形镜对Zernike像差的拟合精度来评价,但不易反映变形镜参数变化和补偿能力的关系。采用高斯型面形影响函数,并用最小二乘法以及Householder变换法,把系数矩阵正交三角化,直接求解拟合系数,计算出各驱动器驱动权重。通过傅立叶变换,得出拟合波前和入射波前对应频率关系。可将变形镜视作空间滤波器,进行入射波前的补偿。结果表明,变形镜对低空间频率波前具有较好的补偿能力,且驱动器密度是波前补偿能力的决定因素,截止频率的变化与波前类型密切相关。     

Combining OWL ontologies using -Connections

The standardization of the Web Ontology Language (OWL) leaves (at least) two crucial issues for Web-based ontologies unsatisfactorily resolved, namely how to represent and reason with multiple distinct, but linked ontologies, and how to enable effective knowledge reuse and sharing on the Semantic Web.In this paper, we present a solution for these fundamental problems based on -Connections. We aim to use -Connections to provide modelers with suitable means for developing Web ontologies in a modular way and to provide an alternative to the owl:imports construct.With such motivation, we present in this paper a syntactic and semantic extension of the Web Ontology language that covers -Connections of OWL-DL ontologies. We show how to use such an extension as an alternative to the owl:imports construct in many modeling situations. We investigate different combinations of the logics , and for which it is possible to design and implement reasoning algorithms, well-suited for optimization.Finally, we provide support for -Connections in both an ontology editor, SWOOP, and an OWL reasoner, Pellet.     

Associative Grammar Combination Operators for Tree-Based Grammars

Polarized unification grammar (PUG) is a linguistic formalism which uses polarities to better control the way grammar fragments interact. The grammar combination operation of PUG was conjectured to be associative. We show that PUG grammar combination is not associative, and even attaching polarities to objects does not make it order-independent. Moreover, we prove that no non-trivial polarity system exists for which grammar combination is associative. We then redefine the grammar combination operator, moving to the powerset domain, in a way that guarantees associativity. The method we propose is general and is applicable to a variety of tree-based grammar formalisms.     

Vibes: A visual language for specifying behavioral requirements of algorithms

Manually verifying the behavior of software systems with respect to a set of requirements is a time-consuming and error-prone task. If the verification is automatically performed by a model checker however, time can be saved, and errors can be prevented. To be able to use a model checker, requirements need to be specified using a formal language. Although temporal logic languages are frequently used for this purpose, they are neither commonly considered to have sufficient usability, nor always naturally suited for specifying behavioral requirements of algorithms. Such requirements can be naturally specified as regular language recognizers such as deterministic finite accepters, which however suffer from poor evolvability: the necessity to re-compute the recognizer whenever the alphabet of the underlying model changes. In this paper, we present the visual language Vibes that both is naturally suited for specifying behavioral requirements of algorithms, and enables the creation of highly evolvable specifications. Based on our observations from controlled experiments with 23 professional software engineers and 21 M.Sc. computer science students, we evaluate the usability of Vibes in terms of its understandability, learnability, and operability. This evaluation suggests that Vibes is an easy-to-use language.     

Theorem proving for intensional logic

For a number of tasks in knowledge representation, and particularly in natural language semantics, it is useful to be able to treat propositions and properties as objects — as items that can appear as arguments of predicates, as things one can quantify over, and so on. Logics that support such intensional operations are notoriously hard to work with. The current paper presents a theorem prover for one such logic, namely, Turner's property theory.     

Knowledge representation for mathematical discovery: Three experiments in graph theory

This paper describes the nature of mathematical discovery (including concept definition and exploration, example generation, and theorem conjecture and proof), and considers how such an intelligent process can be simulated by a machine. Although the material is drawn primarily from graph theory, the results are immediately relevant to research in mathematical discovery and learning.The thought experiment, a protocol paradigm for the empirical study of mathematical discovery, highlights behavioral objectives for machine simulation. This thought experiment provides an insightful account of the discovery process, motivates a framework for describing mathematical knowledge in terms of object classes, and is a rich source of advice on the design of a system to perform discovery in graph theory. The evaluation criteria for a discovery system, it is argued, must include both a set of behavior to display (behavioral objectives) and a target set of facts to be discovered (factual knowledge).Cues from the thought experiment are used to formulate two hierarchies of representational languages for graphy theory. The first hierarchy is based on the superficial terminology and knowledge of the thought experiment. Generated by formal grammars with set-theoretic semantics, this eminently reasonable approach ultimately fails to meet the factual knowledge criteria. The second hierarchy uses declarative expressions, each of which has a semantic interpretation as a stylized, recursive algorithm that defines a class by generating it correctly and completely. A simple version of one such representation is validated by a successful, implemented system called Graph Theorist (GT) for mathematical research in graph theory. GT generates correct examples, defines and explores new graph theory properties, and conjectures and proves theorems.Several themes run through this paper. The first is the dual goals, behavioral objectives and factural knowledge to be discovered, and the multiplicity of their demands on a discovery system. The second theme is the central role of object classes to knowledge representation. The third is the increased power and flexibility of a constructive (generator) definition over the more traditional predicate (tester) definition. The final theme is the importance of examples and recursion in mathematical knowledge. The results provide important guidance for further research in the simulation of mathematical discovery.     

一个基于“恶意对抗”的公平交互机制的研究

由于多代理交互环境中检测机制、仲裁机制的有限性,合法代理将注定要遭受损失。针对上述现象,该文提出了一个恶意对抗机制（Malice-Antagonized Interaction Mechanism,MAIM),即在该机制下,交互代理双方都允许表现出恶意行为,以期实现交互的公平性,为了分析MAIM机制的可行性,文中应用游戏理论对MAIM在几种典型的游戏中实现交互公平性的情况进行了分析和证明。最终得出结论：在完善信息的纯策略游戏中,MAIM无法实现交互的公平性,而在完美信息的混合策略游戏、不完美信息的顺序游戏和同时决策游戏中,能实现交互的公平性。从而从理论上证明了恶意对抗机制的可行性。     

左旋 石英—传感材料的群论分析,空间群不可约表示

本文把群论方法用于分析传感材料左旋α石英,按简便的方法计算了左旋α石英的空间群单、双值扩展不可约表示,得出晶体电子能带简并度结论。