Continuous client-side query evaluation over dynamic linked data

Existing solutions to query dynamic Linked Data sources extend the SPARQL language, and require continuous server processing for each query. Traditional SPARQL endpoints already accept highly expressive queries, so extending these endpoints for time-sensitive queries increases the server cost even further. To make continuous querying over dynamic Linked Data more affordable, we extend the low-cost Triple Pattern Fragments (TPF) interface with support for time-sensitive queries. In this paper, we introduce the TPF Query Streamer that allows clients to evaluate SPARQL queries with continuously updating results. Our experiments indicate that this extension significantly lowers the server complexity, at the expense of an increase in the execution time per query. We prove that by moving the complexity of continuously evaluating queries over dynamic Linked Data to the clients and thus increasing bandwidth usage, the cost at the server side is significantly reduced. Our results show that this solution makes real-time querying more scalable for a large amount of concurrent clients when compared to the alternatives

On principal minors of Bezout matrix

Let $x_1,...,x_{n}$ be real numbers, $P(x)=p_n(x-x_1)...(x-x_n)$, and $Q(x)$ be a polynomial of degree less than or equal to $n$. Denote by $\Delta(Q)$ the matrix of generalized divided differences of $Q(x)$ with nodes $x_1,...,x_n$ and by $B(P,Q)$ the Bezout matrix (Bezoutiant) of $P$ and $Q$. A relationship between the corresponding principal minors, counted from the right-hand lower corner, of the matrices $B(P,Q)$ and $\Delta(Q)$ is established. It implies that if the principal minors of the matrix of divided differences of a function $g(x)$ are positive or have alternating signs then the roots of the Newton's interpolation polynomial of $g$ are real and separated by the nodes of interpolation.Comment: 15 page

Romania and Bulgaria have not been admitted to the Schengen Agreement because of the deep seated anxiety of the treaty’s current members about the regime’s future

Where will the Schengen Agreement be ten years from now? Ruben Zaiotti explores why its signatories are currently hesitant to admit Romania and Bulgaria. He argues that in the wake of the financial and economic crisis the Romanian and Bulgarian governments can only hope that Schengen club’s chronic anxiety can be channelled against someone else

De sacra militia contra iconomachos : civic strategies to counter iconoclasm in the Low Countries (1566)

Although the iconoclastic scare must have been enormous and the actual impact of the attacks of summer and autumn 1566 can hardly be exaggerated, the Beeldenstorm was not as comprehensive as it seemed to contemporaries and subsequent historians. Indeed, a considerable number of important cities in the Habsburg Netherlands actually managed to ward off destruction, but until now their role has hardly been studied. The aim of this article is twofold: first, it seeks to chart the cities in question. Second, it analyses the preventive measures that they took against the violence. In so doing, it nuances the idea of the Beeldenstorm as an all-destructive wave, and provides insights into the dynamics of the Iconoclastic Fury. More specifically, the cliché that the passivity of magistrates was the main reason for all losses seems in need of considerable revision

The Willmore flow of Hopf-tori in the 33-sphere

In this article the author investigates flow lines of the classical Willmore flow, which start moving in a parametrization of a Hopf-torus in $\mathbb{S}^3$. We prove that any such flow line of the Willmore flow exists globally, in particular does not develop any singularities, and subconverges to some smooth Willmore-Hopf-torus in every $C^{m}$-norm. Moreover, if in addition the Willmore-energy of the initial immersion $F_0$ is required to be smaller than the threshold $8 \, \sqrt{\frac{\pi^3}{3}}$, then the unique flow line of the Willmore flow, starting to move in $F_0$, converges fully to a conformal image of the standard Clifford-torus in every $C^{m}$-norm, up to time dependent, smooth reparametrizations. Key instruments for the proofs are the equivariance of the Hopf-fibration $\pi:\mathbb{S}^3 \to \mathbb{S}^2$ w.r.t. the effect of the $L^2$-gradient of the Willmore energy applied to smooth Hopf-tori in $\mathbb{S}^3$ and to smooth closed regular curves in $\mathbb{S}^2$, a particular version of the Lojasiewicz-Simon gradient inequality, and a certain mathematical bridge between the Euler-Lagrange equation of the elastic energy functional and a particular class of elliptic curves over $\mathbb{C}$