Centre de documentation
scientifique

Multi-way distance joins queries in spatial databases / A. Corral in Geoinformatica, vol 8 n° 4 (December 2004)  

Public [article]  inGeoinformatica > vol 8 n° 4 (December 2004) . - pp 373 - 402 Titre : Multi-way distance joins queries in spatial databases Type de document : Article/Communication Auteurs : A. Corral, Auteur ; Y. Manolopoulos, Auteur ; Y. Theodoridis, Auteur ; M. Vassilakopoulos, Auteur Année de publication : 2004 Article en page(s) : pp 373 - 402 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] arbre-R [Termes IGN] base de données localisées [Termes IGN] graphe [Termes IGN] jointure spatiale [Termes IGN] requête spatiale Résumé : (Auteur) Let a tuple of n objects obeying a query graph (QG) be called the n-tuple. The "Ddistance-value" of this n-tuple is the value of a linear function of distances of the n objects that make up this n-tuple, according to the edges of the QG. This paper addresses the problem of finding the K n-tuples between n spatial datasets that have the smallest Ddistance-values, the so-called K-multi-way distance join query (K-MWDJQ), where each set is indexed by an R-tree-based structure. This query can be viewed as an extension of K-closest-pairs query (K-CPQ) for n inputs. In addition, a recursive non-incremental branch-and-bound algorithm following a depth-first search for processing synchronously all inputs without producing any intermediate result is proposed. Enhanced pruning techniques are also applied to n R-trees nodes in order to reduce the total response time and the number of distance computations of the query. Due to the exponential nature of the problem, we also propose a time-based approximate version of the recursive algorithm that combines approximation techniques to adjust the quality of the result and the global processing time. Finally, we give a detailed experimental study of the proposed algorithms using real spatial datasets, highlighting their performance and the quality of the approximate results. Numéro de notice : A2004-393 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1023/B:GEIN.0000040832.25622.8d En ligne : https://doi.org/10.1023/B:GEIN.0000040832.25622.8d Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26920 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
057-04041	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Performance evaluation of lazy deletion methods in R-trees / A. Nanopoulos in Geoinformatica, vol 7 n° 4 (December 2003)  

Public [article]  inGeoinformatica > vol 7 n° 4 (December 2003) . - pp 337 - 354 Titre : Performance evaluation of lazy deletion methods in R-trees Type de document : Article/Communication Auteurs : A. Nanopoulos, Auteur ; M. Vassilakopoulos, Auteur ; Y. Manolopoulos, Auteur Année de publication : 2003 Article en page(s) : pp 337 - 354 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Information géographique [Termes IGN] arbre-B [Termes IGN] arbre-R [Termes IGN] base de données Résumé : (Auteur) Motivated by the way R-trees are implemented in commercial databases systems, in this paper we examine several deletion techniques for R-trees. In particular, in commercial systems R-tree entries are mapped onto relational tables, which implement their own concurrency protocols on top of existing table-level concurrency mechanisms, In analogy, the actual industrial implementations of B-trees do not apply the well-known merging procedure from textbooks in case of node underflows, but rather they apply the free-at-empty technique. This way, space is sacrificed for the benefit of faster deletions and less locking operations, whereas the search performance practically remains unaffected. In this context, we examine the efficiency of modifications to the original R-tree deletion algorithm, which relax certain constraints of this algorithm and perform a controlled reorganization procedure according to a specified criterion. We present the modified algorithms and experimental results about the impact of these modifications on the tree quality, the execution time for the deletion operation and the processing time of search queries, considering several parameters. The experimental results indicate that the modified algorithms improve the efficiency of the deletion operation, while they do not affect the quality of the R-tree and its performance with respect to search operations. Numéro de notice : A2003-388 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1025521422319 En ligne : https://doi.org/10.1023/A:1025521422319 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26468 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
057-03041	RAB	Revue	Centre de documentation	En réserve L003	Disponible

On the generation of time-evolving regional data / T. Tzouramanis in Geoinformatica, vol 6 n° 3 (September - November 2002)  

Public [article]  inGeoinformatica > vol 6 n° 3 (September - November 2002) . - pp 207 - 231 Titre : On the generation of time-evolving regional data Type de document : Article/Communication Auteurs : T. Tzouramanis, Auteur ; M. Vissikalopoulos, Auteur ; Y. Manolopoulos, Auteur Année de publication : 2002 Article en page(s) : pp 207 - 231 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Information géographique [Termes IGN] données spatiotemporelles [Termes IGN] modèle conceptuel de données localisées [Termes IGN] repère de référence Résumé : (Auteur) Benchmarking of spatiotemporal databases is an issue of growing importance. In case large real data sets are not available, benchmarking requires the generation of artificial data sets following the realworld behavior of spatial objects that change their locations, shapes and sizes over time. Only a few innovative papers have recently addressed the topic of spatiotemporal data generators. However, all existing approaches do not consider several important aspects of continuously changing regional data. In this report, a new generator, called generator of timeevolving regional data (G-TERD), for this class of data is presented. The basic concepts that determine the function of G-TERD are the structure of complex 21) regional objects, their color, maximum speed, zoom and rotationangle per time slot, the influence of other moving or static objects on the speed and on the moving direction of an object, the position and movement of the sceneobserver, the statistical distribution of each changing factor and finally, time. Apart from these concepts, the operation and basic algorithmic issues of G-TERD are presented. In the framework developed, the user can control the generator response by setting several parameters values. To demonstrate the use of G-TERD, the generation of a number of sample data sets is presented and commented. The source code and a visualization tool for using and testing the new generator are available on the Web. Thus, it is easy for the user to manipulate the generator according to specific application requirements and at the same time to examine the reliability of the underlying generalized data model. Numéro de notice : A2002-203 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1019705618917 En ligne : https://doi.org/10.1023/A:1019705618917 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22118 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
057-02031	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Algorithms for joining R-trees and linear region quadtrees / A. Corral (20/07/1999)  

Public contenu dans Advances in spatial data bases, SSD '99, 6th International Symposium, Hong Kong, China, July 20-23, 1999 / Ralf Hartmut Güting (1999)   Titre : Algorithms for joining R-trees and linear region quadtrees Type de document : Article/Communication Auteurs : A. Corral, Auteur ; M. Vassilakopoulos, Auteur ; Y. Manolopoulos, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 20/07/1999 Conférence : SSD 1999, 6th International Symposium Advances in spatial data bases 20/07/1999 23/07/1999 Hong Kong Chine Proceedings Springer Importance : pp 251 - 269 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] accès aux données localisées [Termes IGN] arbre quadratique [Termes IGN] arbre-R [Termes IGN] base de données localisées [Termes IGN] jointure spatiale [Termes IGN] requête spatiale Résumé : (Auteur) The family of R-trees is suitable for storing various kinds of multidimensional objects and is considered an excellent choice for indexing a spatial database. Region Quadtrees are suitable for storing 2-dimensional regional data and their linear variant is used in many Geographical Information Systems for this purpose. In this report, we present five algorithms suitable for processing join queries between these two successful, although very different, access methods. Two of the algorithms axe based on heuristics that aim at minimizing I/O cost with a limited amount of main memory. We also present the results of experiments performed with real data that compare the I/O performance of these algorithms. Numéro de notice : C1999-060 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Communication DOI : 10.1007/3-540-48482-5_16 En ligne : https://doi.org/10.1007/3-540-48482-5_16 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=65826