Visualizing Spatial Query Results: The Limitations of SQL
Max Egenhofer and Werner Kuhn Visual Database Systems II, Budapest, Hungary,
E. Knuth and L. Wegner (eds.), IFIP Transactions A: Computer Science and Technology, Vol. A-7, North-Holland, pp. 5-18, October 1991.
Abstract
Several extensions to the relational database query language SQL
have been proposed to serve as a spatial query language; however,
they do not sufficiently address how to visualize query results.
This paper investigates the requirements for an ad hoc language
describing the graphical representation of spatial query results
from the perspective of a geographic information system with
frequent map output and assesses several spatial SQL extensions
with respect to their treatment of the graphical representation. It
concludes that the SQL framework is inappropriate for this task at
the user interface.
Max Egenhofer and 
Werner Kuhn