The Kimball Group Reader by Ralph Kimball & Margy Ross & Warren Thornthwaite & Joy Mundy & Bob Becker

Author:Ralph Kimball & Margy Ross & Warren Thornthwaite & Joy Mundy & Bob Becker
Language: eng
Format: epub
ISBN: 9781119216599
Publisher: Wiley
Published: 2015-12-30T00:00:00+00:00

Geographic Query on Standard Databases

It is possible to add spatial analysis semantics to your existing relational databases. ESRI is capable of placing a geographic interpretation layer between the user and any of these databases with its Spatial Database Engine (SDE) product. The charm of SDE is that you don't need to buy a separate database for geographic processing.

SDE can be configured in a variety of modes. The SDE server can directly manage geo-specific tables such as street maps and shapefiles, and at the same time provide virtual links to your own underlying, unmodified tables residing on one of the conventional relational databases. Or SDE can physically alter and populate your underlying tables with geo-specific attributes such as points, lines, and polygons.

SDE exposes an enhanced SQL API to clients, including MapObjects. So within MapObjects, you can construct queries effectively against your normal warehouse data that can determine the relationship between geographic features. Such relationships might be crossings or intersections, shared boundaries or points, or the containment of one feature within another. References to SDE-managed data attributes can be mixed freely within a single SQL expression that is otherwise referring to your normal data. SDE's SQL extensions let you ask complex distance questions, such as the distance between a point location and some other extended boundary defined area. Another difficult distance question is how far a complex, extended area is from a line feature such as a road or a pipeline.

SDE can impose constraints on geographic features such as lines to guarantee at all times that they form a properly constructed network of a certain topology. SDE also manages what ESRI calls dynamic spatial overlay, which splits the spatial analysis operations away from the data retrieval operations while pipelining these operations so that SDE can overlay two data sets without first fully extracting both of them.

SDE defines an architecture as well as a set of spatial query operations. Other vendors, such as IBM and Oracle, have implemented the full set of ESRI SDE query operations while proposing their own software architectures, or in some cases, mixing their own products with ESRI's.

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