Incompleteness of states w.r.t. traces in model checking

Cousot and Cousot introduced and studied a general past/future-time specification language, called

-calculus, featuring a natural time-symmetric trace-based semantics. The standard state-based semantics of the

-calculus is an abstract interpretation of its trace-based semantics, which turns out to be incomplete, that is trace-incomplete, even for finite systems. As a consequence, standard state-based model checking of the

-calculus is incomplete w.r.t. trace-based model checking. This paper shows that any refinement or abstraction of the domain of sets of states induces a corresponding semantics which is still trace-incomplete for any propositional fragment of the

-calculus. This derives from a number of results, one for each incomplete logical/temporal connective of the

-calculus, that characterize the structure of models, i.e., transition systems, whose corresponding state-based semantics of the

-calculus is trace-complete.     

Eine Neue invariante für kontextfreie sprachen

Let G = (V, T, P, S) a c.f. grammar and F(V ? T) the free group generated by V ? T, (

(G) = F(V ? T/P is the quotient of F (V ? T) factorized by the relationsystem generated by P. We prove that (

(G) only depends on L(G) if G has no superflous variables. This means (fx107-1(G) is an invariant of grammar transformations which preserve the language. Each finitely representable group can be represented by a one sided liner grammar G as (

(G).In a straightforward manner one can compute finite basises for the Alexander-ideals of the groups (

(G. This ideals are finitely generated in an quotient of a Polynomring by a finitely generated ideal. Therefore this leads to effective computable necessary conditions for the equivalence of c.f. grammars.     

The oscillation of partial difference equations with continuous arguments

For the partial difference equations

and

we shall obtain sufficient conditions for the oscillation of all solutions of these equations.     

Prefix codes,trees, and automata

We investigate the relations between the tree representation of a prefix code C, its patterns, the minimal automaton

which recognizes $\text{C}{}^1$, and the homomorphic images of the underlying algebra of

. These relations provide us with an appealing formulation which allows us to state (and eventually solve) some problems concerning the structure of prefix codes and therefore the structure of trees.     

Ultrawrap: SPARQL execution on relational data

The Semantic Web’s promise of web-wide data integration requires the inclusion of legacy relational databases,¹ i.e. the execution of SPARQL queries on RDF representation of the legacy relational data. We explore a hypothesis: existing commercial relational databases already subsume the algorithms and optimizations needed to support effective SPARQL execution on existing relationally stored data. The experiment is embodied in a system, Ultrawrap, that encodes a logical representation of the database as an RDF graph using SQL views and a simple syntactic translation of SPARQL queries to SQL queries on those views. Thus, in the course of executing a SPARQL query, the SQL optimizer uses the SQL views that represent a mapping of relational data to RDF, and optimizes its execution. In contrast, related research is predicated on incorporating optimizing transforms as part of the SPARQL to SQL translation, and/or executing some of the queries outside the underlying SQL environment.Ultrawrap is evaluated using two existing benchmark suites that derive their RDF data from relational data through a Relational Database to RDF (RDB2RDF) Direct Mapping and repeated for each of the three major relational database management systems. Empirical analysis reveals two existing relational query optimizations that, if applied to the SQL produced from a simple syntactic translations of SPARQL queries (with bound predicate arguments) to SQL, consistently yield query execution time that is comparable to that of SQL queries written directly for the relational representation of the data. The analysis further reveals the two optimizations are not uniquely required to achieve a successful wrapper system. The evidence suggests effective wrappers will be those that are designed to complement the optimizer of the target database.     

基于空值修复的数据库一致性查询方法*

完整性约束常用来定义数据库的数据语义,违反约束的数据库实例为不一致数据库,返回含有不一致结果的查询称为不一致查询。一致性查询目的在于不修改数据库实例而从不一致数据库获取满足约束的查询结果,已有方法因其支持的约束类型有限或计算复杂度高而影响其应用范围。提出了一种基于空值修复的数据库一致性查询方法,首先将原始完整性约束转换为与查询相关的统一约束,然后根据统一约束对原SQL查询进行查询重写,重写后的查询将不一致属性值当做空值来处理以获得满足完整性约束的结果。系统实现与实验证明,该方法在多种完整性约束类型与SQL     

Integral operator and starlike functions

We define a class of univalent starlike functions and consider the following integral operator:

It is well known that, if ƒ is starlike, then F is also starlike. We extend this result for a more general class.     

Positive solutions to a nonlinear abel-type integral equation on the whole line

We consider the existence of positive solutions to the nonlinear integral equation

where g is a continuous, nondecreasing function such that g(0) = 0. We show that the equation always has nontrivial solutions and we give a necessary and sufficient condition for the existence of solutions u such that u(x) > − ∞. We also provide a condition which ensures that all the nontrivial solutions experience the blow-up behaviour.     

A reciprocal difference equation with maximum

We consider positive solutions of the following difference equation:

We prove that every positive solution is eventually periodic.     

Oscillation of solutions for second-order nonlinear difference equations with nonlinear neutral term

Some Riccati type difference inequalities are given for the second-order nonlinear difference equations with nonlinear neutral term.

and using these inequalities, we obtain some oscillation criteria for the above equation.     

An improved adaptive differential evolution algorithm for continuous optimization

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Some theoretical aspects of fuzzy-relation equations describing fuzzy systems

This paper contains some theoretical results on fuzzy-relation equations and applications to analysis of fuzzy systems as well as identification and control problems. If A_i, 1 ? i ? k, are fuzzy inputs, B is a fuzzy output, and R is a fuzzy relation describing the system, the above problems are illustrated by means of a max-min multidimensional equation of type $\text{B = A}{}_1\textcolor{red}{}\text{…}\textcolor{red}{}\text{A}{}_{\mathrm{k}}\textcolor{red}{}\text{R}$. Furthermore, we investigate some properties of fuzzy systems described by fuzzy-relation equations, focusing our attention on energy and entropy measures of fuzziness of solutions of the class of equations under discussion.     

Testing juntas

We show that a boolean valued function over n variables, where each variable ranges in an arbitrary probability space, can be tested for the property of depending on only J of them using a number of queries that depends only polynomially on J and the approximation parameter ε. We present several tests that require a number of queries that is polynomial in J and linear in ε⁻¹. We show a non-adaptive test that has one-sided error, an adaptive version of it that requires fewer queries, and a non-adaptive two-sided version of the test that requires the least number of queries. We also show a two-sided non-adaptive test that applies to functions over n boolean variables, and has a more compact analysis.We then provide a lower bound of on the number of queries required for the non-adaptive testing of the above property; a lower bound of for adaptive algorithms naturally follows from this. In establishing this lower bound we also prove a result about random walks on the group Z^q₂ that may be interesting in its own right. We show that for some , the distributions of the random walk at times t and t+2 are close to each other, independently of the step distribution of the walk.We also discuss related questions. In particular, when given in advance a known J-junta function , we show how to test a function for the property of being identical to up to a permutation of the variables, in a number of queries that is polynomial in J and ε⁻¹.     

Numerical optimum design of elastic annular plates with respect to buckling

Annular plates of fixed volume, under uniform radial edge compression are considered. The plate is divided into N segments of linearly variable or constant thickness. Geometrical constrains for the segment thickness and for the effective stress are assumed. Two types of objective functions are explored: (I) maximum value of critical load at the fixed number of circumferential buckling half-waves j, (II) unimodal optimum design for such a number j that buckling load equals max

. The shooting method is applied to compute the distribution of axial forces in the prebuckling state and the basic buckling load for the plate of variable thickness. The optimal distribution of segment thicknesses Xk for k = 1, …, N are computed by means of Rosenbrock's method with internal penalty function. Results of numerical analysis are reported for the both optimum design problems I and II.     

Answering Count Questions with Structured Answers from Text

In this work we address the challenging case of answering count queries in web search, such as number of songs by John Lennon. Prior methods merely answer these with a single, and sometimes puzzling number or return a ranked list of text snippets with different numbers. This paper proposes a methodology for answering count queries with inference, contextualization and explanatory evidence. Unlike previous systems, our method infers final answers from multiple observations, supports semantic qualifiers for the counts, and provides evidence by enumerating representative instances. Experiments with a wide variety of queries, including existing benchmark show the benefits of our method, and the influence of specific parameter settings. Our code, data and an interactive system demonstration are publicly available at https://github.com/ghoshs/CoQEx and https://nlcounqer.mpi-inf.mpg.de/.     

A reliable algorithm for obtaining positive solutions for nonlinear boundary value problems

In this paper, we propose an algorithm for solving the nonlinear two-point boundary value problem

that has at least one positive solution [1–6] for λ in a compatible interval. Our method stems mainly from combining the decomposition series solution obtained by Adomian decomposition method with Padé approximates. The validity of the approach is verified through illustrative numerical examples     

The range of the iterated matrix adjoint operator

The following inverse problem is considered: for a given n × n real matrix B, does there exist a real matrix A such that

where the classical adjoint operation is intended? The rank of B and the number of applications of the adjoint operator determine the character of this general inverse problem for the iterated adjoint operator. Thus, for given B, the question of interest is whether or not B lies in the range of the iterated matrix adjoint operator. Maple V R5 is used as an aid to obtain results indicated here.     

Numerical computations for singular semilinear elliptic boundary value problems

The paper studies a class of Dirichlet problems with homogeneous boundary conditions for singular semilinear elliptic equations in a bounded smooth domain in

. A numerical method is devised to construct an approximate Green's function by using radial basis functions and the method of fundamental solutions. An estimate of the error involved is also given. A weak solution of the above given problem is a solution of its corresponding nonlinear integral equation. A computational method is given to find the minimal weak solution U, and the critical index λ* (such that a weak solution U exists for λ < λ*, and U does not exist for λ > λ*).     

On universality of concurrent expressions with synchronization primitives

Concurrent expressions are a class of extended regular expressions with a shuffle operator (6) and its closure (

). The class of concurrent expressions with synchronization primitives, called synchronized concurrent expressions, is introduced as an extended model of Shaw's flow expressions. This paper discusses some formal properties of synchronized concurrent expressions from a formal language theoretic point of view. It is shown that synchronized concurrent expressions with three signal/wait operations are universal in the sense that they can simulate any semaphore controlled concurrent expressions and they can describe the class of recursively enumerable sets. Some results on semaphore controlled regular expressions are also included to give a taste of more positive results.