A dynamic specification to automatically debug and correct various divider circuits

This paper presents a formal technique to verify and debug division circuits on fixed point numbers. The proposed technique is based on a reverse-engineering mechanism of obtaining a high level model of the gate level implementation and also introducing an intermediate representation of the specification that makes equivalence checking between two models possible. The main advantage of this representation is the fact that the specification is dynamically updated according to the information obtained from the implementation. At the end, if two updated models are not equivalent, possible bugs can be localized and then corrected automatically by analyzing the difference, if possible. Experimental results show the robustness of the proposed technique in comparison with other contemporary methods in terms of the run time and also show that two orders of magnitude average speedup is obtained.     

钢筋混凝土框架结构施工技术

对多层框架结构施工过程中遇到的技术问题及解决方案进行论述,对做好类似工程的施工技术工作具有借鉴意义。     

Abstract Interaction Objects

The concept of an ‘interactor’ has been introduced by Faconti and Paterno' [6] as an abstraction of an entity in interactive graphics capable of both input and output. However the notion of interaction object need not be confined to graphics systems; it represents a useful structure for thinking and reasoning about the behaviour of interactive systems in general. As part of Esprit Basic Research Action 7040 (Amodeus-2) we are using the concept of interactor, and existing work on state-based processes and agents, to develop a model and theory of interactive systems. In this paper we describe two formal models for interaction objects and sketch how they can be used to build a small vocabulary of operators to support the rigorous specification of a graphics system. Our model differs from the approach of Faconti and Paterno' in that it abstracts away from any specific graphics framework and is thus suited to the level of abstraction demanded by formal approaches to system development.     

日本新建筑标准的结构抗火设计

本的目的是为了说明1998—2000期间日本建筑规程(日本建筑标准)以及相关技术标准的修订。考虑了功能要求后，规程修订趋向于以性能为主。在抗大这一章节中，功能要求指的是在发生火灾时防止结构倒塌以及火势向其他隔问的蔓延，同时还包括防止火势由失火建筑物内部向周围建筑的扩散。为了满足功能上的要求，我们提供了三种方法(A、B、C)。方法A是传统的设计方法，即建筑框架及隔墙采用防火构件。相对于方法A，新近引进了以考虑性能为主的方法B。在方法B中，由一系列设计公式计算出指定部分发生火灾可能产生的后果、结构和边界部分的热反应、构件破坏的临界时间。设计公式应足够简单，以便于建筑工程师和有关官员的使用。由方法B计算出的结果通常是保守的。方法C是一个框架，用最先进的设计方法。规程没有指定采用的设计方法，但是工程上火灾和结构分析的结果只有在全面地考证后才能被行业接受。     

Verifying local stratifiability of logic programs and databases

In this paper, we deal with the problem of verifying local stratifiability of logic programs and databases presented by Przymusinski. The notion of dependency graphs is generalized from representing the priority relation between predicate symbols to representing the priority between atoms. Necessary and sufficient conditions for the local stratifiability of logic programs are presented and algorithms for performing the verification are developed. Finally, we prove that a database DB containing clauses with disjunctive consequents can easily be converted into a logic program P such that DB is locally stratified iff P is locally stratified. Yi-Dong Shen, Dr.: Department of Computer Science, Chongqing University, Chongqing, 630044, P.R. China (Present Address) c/o Ping Ran, Department of Heat Power Engineering, Chongqing UniversityResearch interests: Artificial Intelligence, Deductive Databases, Logic Programming, Non-Monotonic Reasoning, Parallel Processing     

Critique of the Lake Arrowhead Three

The photograph and autobiography of Dr. Leslie Lamport were published in Volume 4, Issue No. 2, 1990 on page 59     

Quantified Computation Tree Logic

Computation Tree Logic (CTL) is one of the most syntactically elegant and computationally attractive temporal logics for branching time model checking. In this paper, we observe that while CTL can be verified in time polynomial in the size of the state space times the length of the formula, there is a large set of reachability properties which cannot be expressed in CTL, but can still be verified in polynomial time. We present a powerful extension of CTL with first-order quantification over sets of reachable states. The extended logic, QCTL, preserves the syntactic elegance of CTL while enhancing its expressive power significantly. We show that QCTL model checking is PSPACE-complete in general, but has a rich fragment (containing CTL) which can be checked in polynomial time. We show that this fragment is significantly more expressive than CTL while preserving the syntactic beauty of CTL.     

适于SoC的统一设计语言SystemVerilog

顺应SoC的发展趋势,Accellera标准组织提议了一个统一设计语言SystemVerilog。本文主要讨论了SystemVerilog的特点、设计优势、现状和未来趋势等,并给出了一些实例。SystemVerilog是C、C 、Superlog和Verilog的混合,它极大地扩展了抽象结构层次的设计建模和验证的能力,是SoC设计的最佳统一语言。     

Modular verification of Ada generics

This paper develops modular verification rules for Ada generics which are proven to be sound and complete. The generic mechanism in Ada allows modules to be parameterized by types, procedures and functions. The modularity property allows a generic to be verified once, and then exported to other modules which assume that it is correct. This requires the generic to have a specification which is used in verifying other modules, but its implementation cannot be used for this purpose. Thus, modular verification cannot be based on removing generics by macro expansion which requires the use of the generic's implementation. The main difficulty with specifying and verifying a generic is that the specification language may need to be extended with a new theory for specifying and reasoning about properties of objects whose type is a parameter to the generic. Such theories must be part of the specification of the generic, and this raises the possibility that the extended specification language may not be expressive, even if it was before the extension. The use of strings in our specification language prevents this from happening, which is proven in the paper; this is a major step toward establishing the completeness of our rules. Modularity also had a large impact on our semantics for programming constructs which is quite different from the usual semantics in the literature, even though it is still based the denotational semantics of Scott and Strachey. The main reason for this is that we had to modify the standard definition of validity. Modularity requires that validity depend on certain internal assertions in a program, such as the precondition of a procedure invoked in the program.     

BIM技术在兰州西客站站房工程中的典型应用

文章以兰州西客站项目中BIM技术的应用为例,探索施工企业在火车站站房类工程中施工流程、工程难点、解决方案、专业化应用等BIM技术的典型应用,为类似工程提供参照意义。通过集中解决土建工程量计算、钢结构屋面网架的二次深化设计和吊装施工模拟等重点难点,进而提高了专业化应用的质量,充分发挥了BIM技术在提高施工企业＂三控三管及协调＂、绿色施工等方面的作用。