Existential Second-Order Logic Over Graphs: A Complete Complexity-Theoretic Classification

Descriptive complexity theory aims at inferring a problem's computational complexity from the syntactic complexity of its description. A cornerstone of this theory is Fagin's Theorem, by which a graph property is expressible in existential second-order logic (ESO logic) if, and only if, it is in NP. A natural question, from the theory's point of view, is which syntactic fragments of ESO logic also still characterize NP. Research on this question has culminated in a dichotomy result by Gottlob, Kolatis, and Schwentick: for each possible quantifier prefix of an ESO formula, the resulting prefix class either contains an NP-complete problem or is contained in P. However, the exact complexity of the prefix classes inside P remained elusive. In the present paper, we clear up the picture by showing that for each prefix class of ESO logic, its reduction closure under first-order reductions is either FO, L, NL, or NP. For undirected, self-loop-free graphs two containment results are especially challenging to prove: containment in L for the prefix $\exists R_1 \cdots \exists R_n \forall x \exists y$ and containment in FO for the prefix $\exists M \forall x \exists y$ for monadic $M$. The complex argument by Gottlob, Kolatis, and Schwentick concerning polynomial time needs to be carefully reexamined and either combined with the logspace version of Courcelle's Theorem or directly improved to first-order computations. A different challenge is posed by formulas with the prefix $\exists M \forall x\forall y$: We show that they express special constraint satisfaction problems that lie in L.Comment: Technical report version of a STACS 2015 pape

Fast Parallel Fixed-Parameter Algorithms via Color Coding

Fixed-parameter algorithms have been successfully applied to solve numerous difficult problems within acceptable time bounds on large inputs. However, most fixed-parameter algorithms are inherently \emph{sequential} and, thus, make no use of the parallel hardware present in modern computers. We show that parallel fixed-parameter algorithms do not only exist for numerous parameterized problems from the literature -- including vertex cover, packing problems, cluster editing, cutting vertices, finding embeddings, or finding matchings -- but that there are parallel algorithms working in \emph{constant} time or at least in time \emph{depending only on the parameter} (and not on the size of the input) for these problems. Phrased in terms of complexity classes, we place numerous natural parameterized problems in parameterized versions of AC$^0$. On a more technical level, we show how the \emph{color coding} method can be implemented in constant time and apply it to embedding problems for graphs of bounded tree-width or tree-depth and to model checking first-order formulas in graphs of bounded degree

Evaluation of ICT Investments toward an Increased Competitiveness

This paper focus on the analysis of the impact of investments in IT industry in the general frame of globalization and the drafting of a model for evaluation so that to address the subject of the theoretization of possible measures and efforts in strategic resource consumption for growing of IT competitiveness. To reap the gains from globalization it is necessary to undergo a process of adjustment as factors of production – such as investment capital – towards the ITC applications. The extent by which e-Government will make a difference and add value is seen as dependent on three factors: strong leadership, management of the ‘digital divide’, and well managed innovation.ITC; e-government; investments; digital divide; Internet.

Common dimensions for entrepreneurship and strategy: the need for strategic entrepreneurship

Research about the combination between strategy and entrepreneurship is in the early stages. While the benefits of combining entrepreneurship and strategy are well established, specific details and relations between common elements of strategy and entrepreneurship as a concept remain under-developed and unsubstantiated. This paper explores the relation between entrepreneurship and strategy. The common conception is that entrepreneurship has a strong effect on strategy process.entrepreneurship, corporate entrepreneurship, opportunities, uncertainty in business, strategic entrepreneurship.

Query complexity of membership comparable sets

AbstractThis paper investigates how many queries to k-membership comparable sets are needed in order to decide all (k+1)-membership comparable sets. For k⩾2 this query complexity is at least linear and at most cubic. As a corollary, we obtain that more languages are O(logn)-membership comparable than truth-table reducible to P-selective sets

Active magnetic bearing for ultra precision flexible electronics production system

Roll-to-roll printing on continuous plastic films could enable the production of flexible electronics at high speed and low cost, but the granularity of feature sizes is limited by the system accuracy. Technologies such as gravure printing and nanoimprint lithography demand a level of rotary motion precision that cannot be achieved with rolling element bearings. Manufacturing tolerances of the rotating parts, thermal drift and process forces in combination with structural compliance add up to additional error motions. In this master by research an active magnetic bearing (AMB) solution is designed for a new, super-sized roll-to-roll flexible electronics production machine, which was so far based on hydrostatic bearings. The magnetic bearing could actively compensate the accumulated synchronous error and maintain high accuracy under all conditions. However, the asynchronous error of a conventional AMB with the required size and power is a problem. In order to reduce the relatively high positioning uncertainty of active magnetic bearings an innovative radial position measurement based on linear, incremental encoders with optical conversion principle is proposed. A commercial encoder scanning head faces a round scale with concentric, coplanar lines on its face. By counting these lines the radial position can be measured. Because such a scale is not readily available, it is made by micro-machining. In experiments, different machining methods are compared. Then a magnetic bearing is built to demonstrate the efficacy of the proposed sensor. As a result, the best measurement noise is 3.5nm at 10kHz and a position uncertainty of approximately 0.25µm has been achieved for the magnetic bearing. These promising results are especially interesting for applications with high precision requirements at low speed of rotation

Benchmarking and Performance Management

The relevance of the chosen topic is explained by the meaning of the firm efficiency concept - the firm efficiency means the revealed performance (how well the firm performs in the actual market environment) given the basic characteristics of the firms and their markets that are expected to drive their profitability (firm size, market power etc.). This complex and relative performance could be due to such things as product innovation, management quality, work organization, some other factors can be a cause even if they are not directly observed by the researcher. The critical need for the management individuals/group to continuously improve their firm/company’s efficiency and effectiveness, the need for the managers to know which are the success factors and the competitiveness determinants determine consequently, what performance measures are most critical in determining their firm’s overall success. Benchmarking, when done properly, can accurately identify both successful companies and the underlying reasons for their success. Innovation and benchmarking firm level performance are critical interdependent activities. Firm level variables, used to infer performance, are often interdependent due to operational reasons. Hence, the managers need to take the dependencies among these variables into account when forecasting and benchmarking performance. This paper studies firm level performance using financial ratio and other type of profitability measures. It uses econometric models to describe and then propose a method to forecast and benchmark performance.benchmarking, competitiveness, innovation, indicators.

The organizational culture role in promoting innovations

The term "culture" represents a system of values, ethical norms, thinking and acting models that are thought and accepted by a collectivity and determine the given social group to act distinctly from other social groups. The issue of organization culture is very often discussed in relation to innovation. The common conception is that an entrepreneurship culture has a strong effect on innovation. A organization culture that creates value supposes respect for people and services which not only satisfy the consumer's needs, but also surpass them.organisation culture, entrepreneurship, innovation, promoter

Computing Shortest Paths in Series-Parallel Graphs in Logarithmic Space

Series-parallel graphs, which are built by repeatedly applying series or parallel composition operations to paths, play an important role in computer science as they model the flow of information in many types of programs. For directed series-parallel graphs, we study the problem of finding a shortest path between two given vertices. Our main result is that we can find such a path in logarithmic space, which shows that the distance problem for series-parallel graphs is L-complete. Previously, it was known that one can compute some path in logarithmic space; but for other graph types, like undirected graphs or tournament graphs, constructing some path between given vertices is possible in logarithmic space while constructing a shortest path is NL-complete

Parallel Multivariate Meta-Theorems

Fixed-parameter tractability is based on the observation that many hard problems become tractable even on large inputs as long as certain input parameters are small. Originally, "tractable" just meant "solvable in polynomial time," but especially modern hardware raises the question of whether we can also achieve "solvable in polylogarithmic parallel time." A framework for this study of parallel fixed-parameter tractability is available and a number of isolated algorithmic results have been obtained in recent years, but one of the unifying core tools of classical FPT theory has been missing: algorithmic meta-theorems. We establish two such theorems by giving new upper bounds on the circuit depth necessary to solve the model checking problem for monadic second-order logic, once parameterized by the tree width and the formula (this is a parallel version of Courcelle\u27s Theorem) and once by the tree depth and the formula. For our proofs we refine the analysis of earlier algorithms, especially of Bodlaender\u27s, but also need to add new ideas, especially in the context where the parallel runtime is bounded by a function of the parameter and does not depend on the length of the input