Ralf Hartmut Güting
Praktische Informatik IV, FernUniversität Hagen D-58084 Hagen, Germany firstname.lastname@example.org
Abstract: We propose a definition of a spatial database system as 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 leastspatial indexing and spatial join methods. Spatial database systems offer the underlying database technology for geographic information systems and other applications. We survey data modeling, querying, data structures and algorithms, and system architecture for such systems. The emphasis is on describing known technology in a coherent manner rather than on listing open problems.
InvitedContribution to a Special Issue on Spatial Database Systems of the VLDB Journal (Vol. 3, No. 4, October 1994)
1 What is a Spatial Database System?
In various fields there is a need to manage geometric, geographic, or spatial data, which means data related to space. The space of interest can be, for example, the two-dimensional abstraction of (parts of) the surface ofthe earth – that is, geographic space, the most prominent example –, a man-made space like the layout of a VLSI design, a volume containing a model of the human brain, or another 3d-space representing the arrangement of chains of protein molecules. At least since the advent of relational database systems there have been attempts to manage such data in database systems. Characteristic for thetechnology emerging to address these needs is the capability to deal with large collections of relatively simple geometric objects, for example, a set of 100 000 polygons. This is somewhat different from areas like CAD databases (solid modeling etc.) where geometric entities are composed hierarchically into complex structures, although the issues are certainly related. Several terms have been used fordatabase systems offering such support like pictorial, image, geometric, geographic, or spatial database system. The terms “pictorial” and “image” database system arise from the fact that the data to be managed are often initially captured in the form of digital raster images (e.g. remote sensing by satellites, or computer tomography in medical applications). The term “spatial database system” hasbecome popular during the last few years, to some extent through the series of conferences “Symposium on Large Spatial Databases (SSD)” held bi-annually since 1989 [Buch89, GünS91, AbO93], and is associated with a view of a database as containing sets of objects in space rather than images or pictures of a space. Indeed, the requirements and techniques for dealing with objects in space that haveidentity and well-defined extents, locations, and relationships are rather different from those for dealing with raster images. It has therefore been suggested to clearly distinguish two classes of systems called spatial database systems and image database systems, respectively [GünB90, Fra91]. Image database systems may include analysis techniques to extract objects in space from images, and offersome spatial database functionality, but are also prepared to store, manipulate and retrieve raster images as discrete entities. In this survey we only discuss spatial database systems in the restricted sense. Several papers in this special issue address image database problems and so complement the survey. What is a spatial database system? We are not aware of a generally accepted definition.The following reflects the author's personal view: (1) A spatial database system is a database system. (2) It offers spatial data types (SDTs) in its data model and query language. (3) It supports spatial data types in its implementation, providing at least spatial indexing and efficient algorithms for spatial join. Let us briefly justify these requirements. (1) sounds trivial, but emphasizes the...