32 research outputs found
Contributions Ă lâOptimisation de RequĂȘtes Multidimensionnelles
Analyser les donnĂ©es consiste Ă choisir un sous-ensemble des dimensions qui les dĂ©criventafin d'en extraire des informations utiles. Or, il est rare que l'on connaisse a priori les dimensions"intĂ©ressantes". L'analyse se transforme alors en une activitĂ© exploratoire oĂč chaque passe traduit par une requĂȘte. Ainsi, il devient primordiale de proposer des solutions d'optimisationde requĂȘtes qui ont une vision globale du processus plutĂŽt que de chercher Ă optimiser chaque requĂȘteindĂ©pendamment les unes des autres. Nous prĂ©sentons nos contributions dans le cadre de cette approcheexploratoire en nous focalisant sur trois types de requĂȘtes: (i) le calcul de bordures,(ii) les requĂȘtes dites OLAP (On Line Analytical Processing) dans les cubes de donnĂ©es et (iii) les requĂȘtesde prĂ©fĂ©rence type skyline
LIPIcs, Volume 261, ICALP 2023, Complete Volume
LIPIcs, Volume 261, ICALP 2023, Complete Volum
LIPIcs, Volume 244, ESA 2022, Complete Volume
LIPIcs, Volume 244, ESA 2022, Complete Volum
Large bichromatic point sets admit empty monochromatic 4-gons
We consider a variation of a problem stated by ErdËos
and Szekeres in 1935 about the existence of a number
fES(k) such that any set S of at least fES(k) points in
general position in the plane has a subset of k points
that are the vertices of a convex k-gon. In our setting
the points of S are colored, and we say that a (not necessarily
convex) spanned polygon is monochromatic if
all its vertices have the same color. Moreover, a polygon
is called empty if it does not contain any points of
S in its interior. We show that any bichromatic set of
n â„ 5044 points in R2 in general position determines
at least one empty, monochromatic quadrilateral (and
thus linearly many).Postprint (published version