Spatial Database Interface Specification

UNISYS TECHNOLOGY UPDATE: UPDATED SPATIAL DATABASE INTERFACE SPECIFICATION FOR THE C PROGRAMMING LANGUAGE Recently, the International Organization for Standardization
(ISO) adopted ISO/IEC 9075-3:1995, "Information technology --
Database languages -- SQL -- Part 3, Call-Level Interface
(SQL/CLI)" as an international standard. This standard defines
the client side programming interface for the database language SQL. Easily mapped to the C programming language, the interface is a popular interface to SQL database systems in the form of the Microsoft(r) ODBC interface for the Microsoft Windows(tm) and Windows NT(tm) Operating Systems.

In conjunction with this, in January 1996, the SQL/Multimedia and Application Packages (SQL/MM) project reached broad consensus on the set of abstract data types to be standardized for spatial data handling found in Part 3: Spatial. SQL/MM--Part 3: Spatial provides abstract data types to collect point, line and polygon geometric primitives into instances of a spatial object. The spatial object may to referenced to the earth's surface and provides a set of operators to manipulate the data. Unisys has taken a leadership role in this standards arena in the US and Internationally by providing resources and time to progress this very important work.

The Spatial Technology Program of Unisys Corporation (Toronto, Ontario, Canada) has just updated its open C API specification based on the database language SQL (ISO/IEC 9075:1992), SQL/CLI
(ISO/IEC 9075-3:1995) and the work done in the SQL/MM standards
effort. This update reflects the latest changes to the working draft of the SQL/MM--Part 3: Spatial Base Document. As a base, the database language SQL and SQL/CLI provide the foundation for the Spatial C-API. Spatial extensions incrementally add the ability to manage spatial information.

This interface defines the data type: ST_SpatialObject from SQL/MM. Like other data types in SQL, it may be used in a column definition of a table and referenced in programs. The ST_SpatialObject is a container that can hold the following geometric primitives: points, polylines, circular arcs and polygons with or without holes.

The database language SQL has been extended to manage the ST_SpatialObject data type. New instances of type ST_SpatialObject may be created using an extensive set of constructor functions. There are spatial predicates such as "overlap" and "contains" to qualify spatial information of interest. There are spatial functions such as "centroid" and "buffer" to create new instances of type ST_SpatialObject; these instances can be used in the same query or returned to the application for further analysis. Metric functions like "length" and "area" are also available.

The language extensions have been folded into a Call Level Interface in the C Programming Language. The CLI interface enables the client to retrieve, insert, update and delete both spatial and non-spatial database information with a single API. In doing so, the database administrator can be confident that the data is safe and secure since this interface is integrated into the security and transaction manager of the DBMS.

With a suite of client side functions, desktop software components can easily manage the spatial information on the network servers. By the use of existing IT standards and by tracking the emerging SQL Multimedia Standards, Unisys is able to provide an interface today that will work with existing applications and future components. These facilities open the window to providing spatial capabilities in your OLAP environment.

For more information, send email to info_at_spatial.unisys.com on the internet.

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Cheers
Mark.