8 research outputs found
Query processing of geometric objects with free form boundarie sin spatial databases
The increasing demand for the use of database systems as an integrating
factor in CAD/CAM applications has necessitated the development of database
systems with appropriate modelling and retrieval capabilities. One essential
problem is the treatment of geometric data which has led to the development of
spatial databases. Unfortunately, most proposals only deal with simple geometric
objects like multidimensional points and rectangles. On the other hand, there has
been a rapid development in the field of representing geometric objects with free
form curves or surfaces, initiated by engineering applications such as mechanical
engineering, aviation or astronautics. Therefore, we propose a concept for the realization
of spatial retrieval operations on geometric objects with free form
boundaries, such as B-spline or Bezier curves, which can easily be integrated in
a database management system. The key concept is the encapsulation of geometric
operations in a so-called query processor. First, this enables the definition of
an interface allowing the integration into the data model and the definition of the
query language of a database system for complex objects. Second, the approach
allows the use of an arbitrary representation of the geometric objects. After a
short description of the query processor, we propose some representations for free
form objects determined by B-spline or Bezier curves. The goal of efficient query
processing in a database environment is achieved using a combination of decomposition
techniques and spatial access methods. Finally, we present some experimental
results indicating that the performance of decomposition techniques is
clearly superior to traditional query processing strategies for geometric objects
with free form boundaries
A storage and access architecture for efficient query processing in spatial database systems
Due to the high complexity of objects and queries and also due to extremely
large data volumes, geographic database systems impose stringent requirements on their
storage and access architecture with respect to efficient query processing. Performance
improving concepts such as spatial storage and access structures, approximations, object
decompositions and multi-phase query processing have been suggested and analyzed as
single building blocks. In this paper, we describe a storage and access architecture which
is composed from the above building blocks in a modular fashion. Additionally, we incorporate
into our architecture a new ingredient, the scene organization, for efficiently
supporting set-oriented access of large-area region queries. An experimental performance
comparison demonstrates that the concept of scene organization leads to considerable
performance improvements for large-area region queries by a factor of up to 150
Query processing of spatial objects: Complexity versus Redundancy
The management of complex spatial objects in applications, such as geography and cartography,
imposes stringent new requirements on spatial database systems, in particular on efficient
query processing. As shown before, the performance of spatial query processing can be improved
by decomposing complex spatial objects into simple components. Up to now, only decomposition
techniques generating a linear number of very simple components, e.g. triangles or trapezoids, have
been considered. In this paper, we will investigate the natural trade-off between the complexity of
the components and the redundancy, i.e. the number of components, with respect to its effect on
efficient query processing. In particular, we present two new decomposition methods generating
a better balance between the complexity and the number of components than previously known
techniques. We compare these new decomposition methods to the traditional undecomposed representation
as well as to the well-known decomposition into convex polygons with respect to their
performance in spatial query processing. This comparison points out that for a wide range of query
selectivity the new decomposition techniques clearly outperform both the undecomposed representation
and the convex decomposition method. More important than the absolute gain in performance
by a factor of up to an order of magnitude is the robust performance of our new decomposition
techniques over the whole range of query selectivity
Um benchmark voltado a analise de desempenho de sistemas de informações geograficas
Orientador: Geovane Cayres MagalhãesDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Ciencia da ComputaçãoResumo: A enorme quantidade e a natureza dos dados armazenados por aplicações que utilizam sistemas de informações geográficas (SIGs) implicam em alterações ou extensões nos métodos de acesso, otimizadores de consulta e linguagens de consulta estabelecidos para sistemas gerenciadotes de banco de dados (SGBDs) convencionais. Com isto, diferentes soluções têm sido apresentadas, tornando-se imprescindível a criação de algum mecanismo que possa medir a eficiência destas soluções para auxiliar o direcionamento de futuros trabalhos de pesquisas. Para tal propósito é utilizada, nesta dissertação, a técnica experimental de benchmark.
Esta dissertação propõe a carga de trabalho e caracteriza os dados de um benchmark voltado à análise de desempenho de SIGs. A carga de trabalho do benchmark é composta por um conjunto de transações primitivas, especificadas em alto nível, que podem ser utilizadas para a formação de transações mais complexas. Estas transações primitivas são predominantemente orientadas aos dados espaciais, sendo, a priori, independentes do formato de dados utilizado (raster ou vetorial). A caracterização dos dados do benchmark foi efetuada em termos dos tipos de dados necessários para a representação de aplicações georeferenciadas, e adicionalmente procedimentos para se realizar a geração de dados sintéticos. Finalmente, uma aplicação alvo utilizando dados sintéticos foi definida com a finalidade de validar o benchmark proposto.Abstract: Geographical Information Systems (GIS) de ai with data that are special in nature and size. Thus, the technologies developed for conventional data base systems such as access methods, query optimizers and languages, have to be modified in order to satisfy the needs of a GIS. These modifications, embedded in several GIS, or being proposed by research projects, need to be evaluated. This thesis proposes mechanisms for evaluating GIS based on benchmarks.
The benchmark is composed of a workload to be submitted to the GIS being analysed and data characterizing the information. The workload is made of a set of primitive transactions that can be. combined in order to derive transactions of any degree of complexity. These primitive transactions are oriented to spatial data but not dependent on the way they are represented (vector or raster). The benchmark data base characterization was defined in terms of the types of data required by applications that use georeferencing, and by the need to generate complex and controlled artificial data. The proposed technique and methods were used to show how to create the transactions and the data for a given application.MestradoMestre em Ciência da Computaçã