Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Computer science & Finite element method. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

Comparative Analysis of Five XML Query Languages

Abstract: XML is becoming the most relevant new standard for data representation and exchange on the WWW. Novel languages for extracting and restructuring the XML content have been proposed, some in the tradition of database query languages (i.e. SQL, OQL), others more closely inspired by XML. No standard for XML query language has yet been decided, but the discussion is ongoing within the World Wide Web Consortium and within many academic institutions and Internet-related major companies. We present a comparison of five, representative query languages for XML, highlighting their common features and differences.

Spin-orbit coupling in the Mott insulator Ca2RuO4

Abstract: O $1s$ x-ray absorption study of the Mott insulator ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{4}$ shows that the orbital population of the $4d$ ${t}_{2g}$ band dramatically changes with temperature. In addition, spin-resolved circularly polarized photoemission study of ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{4}$ shows that a substantial orbital angular momentum is induced in the Ru $4d$ ${t}_{2g}$ band. Based on the experimental results and model Hartree-Fock calculations, we argue that the cooperation between the strong spin-orbit coupling in the Ru $4d$ ${t}_{2g}$ band and the small distortion of the ${\mathrm{RuO}}_{6}$ octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.

A Saint-Venant type principle for Dirichlet forms on discontinuous media

Abstract: We consider certain families of Dirichlet forms of diffusion type that describe the variational behaviour of possibly highly nonhomogeneous and nonisotropic bodies and we prove a structural Harnack inequality and Saint Venant type energy decays for their local solution. Estimates for the Green functions are also considered.

Estimating the Selectivity of Spatial Queries Using the `Correlation' Fractal Dimension

Abstract: We examine the estimation of selectivities for range and spatial join queries in real spatial databases. As we have shown earlier [FK94], real point sets: (a) violate consistently the “uniformity” and “independence” assumptions, (b) can often be described as “fractals”, with non-integer (fractal) dimension. In this paper we show that, among the infinite family of fractal dimensions, the so called “Correlation Dimension” Dz is the one that we need to predict the selectivity of spatial join. The main contribution is that, for all the real and synthetic point-sets we tried, the average number of neighbors for a given point of the point-set follows a power law, with LI& as the exponent. This immediately solves the selectivity estimation for spatial joins, as well as for “biased” range queries (i.e., queries whose centers prefer areas of high point density). We present the formulas to estimate the selectivity for the biased queries, in&ding an integration constant (KLshape,) for each query shape. Finally, we show results on real and synthetic point sets, where our formulas achieve very low relative errors (typically about lo%, versus 40%-100% of the uniformity assumption).