Query Processing in Spatial Databases

IntroductIon Spatial data management has been an active area of intensive research for more than two decades. In order to support spatial objects in a database system several important issues must be taken into account such as: spatial data models, indexing mechanisms and efficient query processing. A spatial database system (SDBS) is a database system that offers spatial data types in its data model and query language and supports spatial data types in its implementation, providing at least spatial indexing and efficient spatial query processing (Güting, 1994). The main reason that has caused the active study of spatial database management systems (SDBMS) comes from the needs of the existing applications such as geographical information systems (GIS), computer-aided design (CAD), very large scale integration design (VLSI), multimedia information systems (MIS), data warehousing, multi-criteria decision making, location-based services, etc. Some of the most important companies in the commercial database industry (Oracle, Infor-mix, Autodesk, etc.) have products specifically designed to manage spatial data. Moreover, re-0 Query Processing in Spatial Databases search prototypes as Postgres and Paradise offer the possibility to handle spatial data. The main functionality provided by these products includes a set of spatial data types such as the point, line, polygon and region; and a set of spatial operations, including intersection, enclosure and distance. The performance enhancement provided by these operations includes spatial access methods and query algorithms over such indexes (e.g. spatial range queries, nearest neighbor search, spatial joins, etc). We must also cite the Open Geographic Information Systems (OGIS) consortium (http://www.opengis.org/), which has developed a standard set of spatial data types and operations and SQL3/SQL99, which is an object-relational query language that provides the use of spatial types and operations. In a spatial database system, the queries are usually expressed in a high-level declarative language such as SQL; therefore specialized database software has to map the query in a sequence of spatial operations supported by spatial access methods (Shekhar & Chawla, 2003). Spatial query processing refers to the sequence of steps that a SDBMS will initiate to execute a given spatial query. The main target of query processing in the database field is to process the query accurately and quickly (consuming the minimum amount of time and resources on the computer), by using both efficient representations and efficient search algorithms. Query processing in a spatial environment focuses on the design of efficient algorithms for spatial operators (e.g. selection operations, …