9/28/2007IVOA Interop1 Implementing the Region Syntax A.Szalay, T.Budavari, P.Dowler, +ADQL Working Group

9/28/2007IVOA Interop2 Function-Based Approach Region is an object that has –Constructors –Properties (area) –Operators Implemented in SQL Server 2005, using the Spherical library (C# + SQL) built for SDSS and the NVO Footprint Service

9/28/2007IVOA Interop3 Similar to Existing GIS Systems SpatialWare (MapInfo) uses the same technique but with lots of functions Geometry datatypes –Point, Line, PolyLine, Polygon, Arc, … Constructors –Circle, Box, Polygon,… Full set operators More detailed topological relations –Contain, Outside, Overlaps, Adjacent, … Buffer Cast –AsText

9/28/2007IVOA Interop4 Steps Create a Region schema (namespace) Define constructors –Region, Circle, Rectangle Define properties –Area Operators –Contains, Intersects, ToString Support –Distance

9/28/2007IVOA Interop5 Lessons SQL-92 functions with variable number of arguments (Polygon) not allowed –Use the Region(string) to build these No boolean datatype in SQL-92 –Use bit (0,1) and explicit comparisons Contains is protected in T-SQL (freetext) –Need to write it as Region.[Contains] Distance function was trivial

9/28/2007IVOA Interop6 Immediate Questions Units? –Angles: degrees –Area: square degrees –Distances: degrees GIS Compatibility? –Contains-> Contain –Intersects -> Overlap –ToString -> AsText –Distance -> SphericalDistance

9/28/2007IVOA Interop7 Operator Extensions Later? Output is Region type –Intersection(r1,r2) –Difference(r1,r2) –Union(r1,r2) –Buffer(r1, delta)