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1.
Theory of Computing Systems - We study automatic equivalence and nested equivalence structures. The goal is to compare and contrast these automatic structures with computable equivalence and nested...  相似文献   

2.
XML文档的范式   总被引:7,自引:1,他引:7  
给出了 XML函数依赖、部分函数依赖和传递函数依赖的概念 ,然后据此提出了三种 XML范式 :1XNF、2 XNF和 3XNF.提出了 DTD无损联接分解的概念 ,给出了两个把 DTD无损联接地分解成 2 XNF和 3XNF的算法  相似文献   

3.
We describe and verify an elegant equivalence checker for regular expressions. It works by constructing a bisimulation relation between (derivatives of) regular expressions. By mapping regular expressions to binary relations, an automatic and complete proof method for (in)equalities of binary relations over union, composition and (reflexive) transitive closure is obtained. The verification is carried out in the theorem prover Isabelle/HOL, yielding a practically useful decision procedure.  相似文献   

4.
Using the CREP system we show that matrix representations of representation-finite algebras can be transformed into normal forms consisting of (0, 1)-matrices.  相似文献   

5.
给出了XML间接函数依赖和传递函数依赖的概念,据此提出了以DTD为模式的XML文档的一种范式XMLNF,它可以消除XML文档中由于间接函数依赖和传递函数依赖所引起的数据冗余,给出了把DTD无损联接地分解成XMLNF的规范化方法.  相似文献   

6.
The last open problem regarding the modularity of the fundamental properties of Term Rewriting Systems concerns the property of uniqueness of normal forms w.r.t. reduction (UN). In this article we solve this open problem, showing that UNis modular for left-linear Term Rewriting Systems. The novel “pile and delete” technique here introduced allows for quite a short proof, and is of independent interest in the study of modular properties. Moreover, we also study the modularity of consistency w.r.t. reduction (CON), showing its modularity for left-linear Term Rewriting Systems.  相似文献   

7.
8.
Short Conjunctive Normal Forms in Finitely Valued Logics   总被引:1,自引:0,他引:1  
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9.
Transfinite semantics is a semantics according to which program executions can continue working after an infinite number of steps. Such a view of programs can be useful in the theory of program transformations.So far, transfinite semantics have been succesfully defined for iterative loops. This paper provides an exhaustive definition for semantics that enable also infinitely deep recursion.The definition is actually a parametric schema that defines a family of different transfinite semantics. As standard semantics also match the same schema, our framework describes both standard and transfinite semantics in a uniform way.All semantics are expressed as greatest fixpoints of monotone operators on some complete lattices. It turns out that, for transfinite semantics, the corresponding lattice operators are cocontinuous. According to Kleene’s theorem, this shows that transfinite semantics can be expressed as a limit of iteration which is not transfinite.  相似文献   

10.
We prove that in all but one case the normal form of a real or complex Hamiltonian matrix which is irreducible and appropriately normalized can be computed by Lie series methods in formally the same manner as one computes the normal form of a nonlinear Hamiltonian function. Calculations are emphasized; the methods are illustrated with detailed examples, and for the sake of completeness the exceptional case is also reviewed and illustrated. Alternate methods are also discussed, along with detailed examples.  相似文献   

11.
We consider the model checking problem for FLC, a modal fixpoint logic capable of defining non-regular properties. This paper presents a refinement of a symbolic model checker and discusses how to parallelise this algorithm. It reports on a prototype implementation of the algorithm in Glasgow Parallel Haskell (GpH) and its performance on a cluster of workstations.  相似文献   

12.
In this paper, we present a translator from a relevant subset of SQL into relational algebra. The translation is syntax-directed, with translation rules associated with grammar productions; each production corresponds to a particular type of SQL subquery.  相似文献   

13.
文中利用严格等价函数提出一种基于区间二型模糊熵的图像阈值分割方法.首先基于公理化定义,利用严格定价函数提出一种区间二型模糊熵的构建方法,由此可以得到多个不同的模糊熵计算表达式;然后通过理论分析给出了利用最小化模糊熵准则选取最优阈值的方法.实验结果表明,与现有的其他模糊阈值分割法和改进的2维Otsu法等相比,该方法的分割更加准确,运行时间更少,具有更广泛的适应性.  相似文献   

14.
三值逻辑函数RDSOP形式的代数理论和T门实现   总被引:2,自引:0,他引:2  
姜恩华  姜文彬 《计算机学报》2007,30(7):1132-1137
三值逻辑函数简化的不相交SOP(RDSOP)形式是一种很有用的代数形式,研究表明,它在T门网络的设计和化简方面有重要应用.利用三值格代数的基本运算和主要性质,讨论了三值函数RDSOP形式的代数理论和算法,并给出了应用实例.利用以三值T门网络可以实现任意三值逻辑函数的原理,提出了基于RDSOP形式的三值T门网络最小化设计的一种方法,并给出了实例.从给出的实例可以看出,该方法是有效且可行的.  相似文献   

15.
16.
A geometric characterization of a class of square invertible nonlinear systems that can be molded into a normal form by a global diffeomorphism is detailed. Then additional conditions are fashioned that permit the implementation of the recursive design method known as “backstepping.” Date received: November 12, 1997. Date revised: December 2, 1998.  相似文献   

17.
In this paper, I am considering a filtration equation, and by using Ovsiannikov's method, I intend to construct the most general equivalence algebra. Moreover, some algorithms are performed in order to extend the principal algebra.  相似文献   

18.
Students meeting their first serious course in abstract algebra commonly experience difficulty understanding many of the basic concepts. This makes it very hard for them to interpret and generate proofs. The first step in reaching an understanding of such concepts is often best achieved by constructing and manipulating instances in particular algebraic structures. Computer algebra systems open up the possibility of students being able to experiment rapidly and conveniently with such concepts in a variety of structures having non-trivial size and complexity. The new Magma computer algebra system has a syntax and semantics based directly on fundamental algebraic notions, and consequently should provide an appropriate learning environment for those branches of mathematics that are heavily algebraic in nature. This paper describes the development of Magma-based exercises and a course methodology that utilizes Magma as a key learning tool in a Pass-level Rings and Fields course given at the University of Sydney.  相似文献   

19.
Current MIMD computers support the execution of data parallel programs by providing a tree network to perform fast barrier synchronizations. However, there are two major limitations to using tree networks: The first arises due to control nesting in programs, and the second arises when the MIMD computer needs to run several programs simultaneously. First, we present two hardware barrier synchronization schemes which can support deep levels of control nesting in data parallel programs. Hardware barriers are usually an order of magnitude faster than software implementations. Since large data parallel programs often have several levels of nested barriers, these schemes provide significant speedups in the execution of such programs on MIMD computers. The first scheme performs code transformations and uses two single-bit-trees to implement unlimited levels of nested barriers. However, this scheme increases the code size. The second scheme uses a more expensive integer-tree to support an exponential number of nesting levels without increasing the code size: we-show that up to n nested barriers can be supported by a network with bisection bandwidth O(log n) and a latency of O(log p log n) gate delays. Using tree network hardware already available on commercial MIMD computers, this scheme can support more than four billion levels of nesting. Second, we present a design for a barrier synchronization network that is free from the partitioning constraints imposed by barrier trees. When the MIMD computer is partitioned among several jobs, then, rather than barrier synchronizations, we desire multiple disjoint barrier synchronizations (MDBSs), where processors within each partition barrier synchronize among themselves without interfering with other partitions. Barrier trees can be adapted to handle MDBSs, but only if the partitions are constrained to be of very special sizes and shapes. These stringent constraints on partitioning often run contrary to other important considerations, such as the contiguity of the processors of each partition within the data network. Our MDBS network design allows for any number of partitions of any size and shape, as long as the processors comprising each partition are contiguous in the data network.  相似文献   

20.
The access control problem in computer security is fundamentally concerned with the ability of system entities to see, make use of, or alter various system resources. We provide a mathematical framework for modelling and reasoning about (distributed) systems with access control. This is based on a calculus of resources and processes together with a Hennessy–Milner-style modal logic, based on the connectives of bunched logic, for which an appropriate correspondence theorem obtains. As a consequence we get a consistent account of both operational behaviour and logical reasoning for systems with access control features. In particular, we are able to introduce a process combinator that describes, as a form of concurrent composition, the action of one agent in the role of another, and provide a logical characterization of this operator via a modality ‘says’. We give a range of examples, including analyses of co-signing, roles, and chains of trust, which illustrates the utility of our mathematical framework.  相似文献   

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