Homotopic rectilinear routing with few links and thick edges

We study the problem of finding non-crossing thick minimum-link rectilinear paths homotopic to a set of input paths in an environment with rectangular obstacles. This problem occurs in the context of map schematization under geometric embedding restrictions, for example, when schematizing a highway network for use as a thematic layer. We present a 2-approximation algorithm that runs in O(n3 +kin log n + kout) time, where n is the total number of input paths and obstacles and kin and kout are the total complexities of the input and output paths, respectively. Our algorithm not only approximates the minimum number of links, but also minimizes the total length of the paths. An approximation factor of 2 is optimal when using smallest paths as lower bound

Algorithms for necklace maps

Necklace maps visualize quantitative data associated with regions by placing scaled symbols, usually disks, without overlap on a closed curve (the necklace) surrounding the map regions. Each region is projected onto an interval on the necklace that contains its symbol. In this paper we address the algorithmic question how to maximize symbol sizes while keeping symbols disjoint and inside their intervals. For that we reduce the problem to a one-dimensional problem which we solve efficiently. Solutions to the one-dimensional problem provide a very good approximation for the original necklace map problem. We consider two variants: Fixed-Order, where an order for the symbols on the necklace is given, and Any-Order where any symbol order is possible. The Fixed-Order problem can be solved in O(n log n) time. We show that the Any-Order problem is NP-hard for certain types of intervals and give an exact algorithm for the decision version. This algorithm is fixed-parameter tractable in the thickness K of the input. Our algorithm runs in O(n log n + n2K4K) time which can be improved to O(n log n + nK2K) time using a heuristic. We implemented our algorithm and evaluated it experimentally. Keywords: Necklace maps; scheduling; automated cartograph

Internationale politieke economie: herijking van de studie naar internationale politiek

Internationale Politieke Economie (IPE) is een nieuw vakgebied dat een zekere integratie voorstaat van Internationale Betrekkingen, Internationale Economische Betrekkingen, Politicologie en Bestuurskunde. Het is een terrein dat zich goed leent om de wisselwerking van verschijnselen op subnationaal, nationaal en internationaal niveau te analyseren. Dit artikel geeft een oeverzicht van de recente ontwikkelingen op dit vakgebied en signaleert de mogelijkheden en beperkingen van IPE

The politics of international norms: Subsidiarity and the imperfect competence regime of the Europenean Union

Contains fulltext : 159968.pdf (publisher's version ) (Closed access)Theories on the role of norms in international relations generally neglect the possibility that after their adoption a new battle over their precise meaning ensues, especially when a norm remains vague and illusive. Norm implementation is not only a matter of internalization and compliance, but also of redefinition. Building on insights from rationalist and constructivist approaches, this article advances the idea of recurrent battles for and over norms in international politics. It argues that the analytical tools of international regime theory are instrumental in tracking such battles. This framework is applied to the history and role of subsidiarity as a norm in the competence regime of the European Union between 1991 and 2005. Its main finding is that the issue of subsidiarity was not a matter of norm internalization, but concerned a recurrent battle between old and newly empowered actors over its precise meaning, eventually favouring the member states' prerogative.22 p

Trace checking of Metric Temporal Logic with Aggregating Modalities using MapReduce

Modern complex software systems produce a large amount of execution data, often stored in logs. These logs can be analyzed using trace checking techniques to check whether the system complies with its requirements specifications. Often these specifications express quantitative properties of the system, which include timing constraints as well as higher-level constraints on the occurrences of significant events, expressed using aggregate operators. In this paper we present an algorithm that exploits the MapReduce programming model to check specifications expressed in a metric temporal logic with aggregating modalities, over large execution traces. The algorithm exploits the structure of the formula to parallelize the evaluation, with a significant gain in time. We report on the assessment of the implementation - based on the Hadoop framework - of the proposed algorithm and comment on its scalability.Comment: 16 pages, 6 figures, Extended version of the SEFM 2014 pape

A framework for algorithm stability

We say that an algorithm is stable if small changes in the input result in small changes in the output. Algorithm stability plays an important role when analyzing and visualizing time-varying data. However, so far, there are only few theoretical results on the stability of algorithms, possibly due to a lack of theoretical analysis tools. In this paper we present a framework for analyzing the stability of algorithms. We focus in particular on the tradeoff between the stability of an algorithm and the quality of the solution it computes. Our framework allows for three types of stability analysis with increasing degrees of complexity: event stability, topological stability, and Lipschitz stability. We demonstrate the use of our stability framework by applying it to kinetic Euclidean minimum spanning trees