Operators on spatial components ..and the intersection operator creates a new spatial component a a C intersection(a, b)= intersection (a, c) 2021/8/25
2021/8/25 11 Operators on spatial components ◼ ..and the ‘intersection’ operator creates a new spatial component a b c a intersection(a,b)= intersection(a,c)=
Operators on themes Projection a List just the names and spatial components of all countries Restriction a Select those rivers with length greater than 100 km Union a Form a new theme containing all geographic objects from two input themes(removing duplicates) Set difference a Form a new theme containing all geographic objects present in the first, but not in the second input theme 2021/8/25
2021/8/25 12 Operators on themes ◼ Projection ❑ ‘List’ just the names and spatial components of all countries. ◼ Restriction ❑ Select those rivers with length greater than 100 km ◼ Union ❑ Form a new theme containing all geographic objects from two input themes (removing duplicates) ◼ Set difference ❑ Form a new theme containing all geographic objects present in the first, but not in the second input theme
Operators on themes Spatial join a Form a new theme containing new objects For every pair of objects, one from each theme, such that their spatial components overlap a .. concatenate the non-spatial attributes constructing new spatial components using the intersection operator on the spatial components of the pair of objects 2021/8/25
2021/8/25 13 Operators on themes ◼ Spatial Join ❑ Form a new theme containing new objects: ◼ For every pair of objects, one from each theme, such that their spatial components overlap… ◼ …concatenate the non-spatial attributes,… ◼ …constructing new spatial components using the intersection operator on the spatial components of the pair of objects
Query language 2021/8/25 14
2021/8/25 14 Query Language
Query language for Spatial database EXtending sql for spatial data a Motivation SQL has simple atomic data-types, like integer dates and string Not convenient for spatial data and queries a Spatial data(e.g polygons)is complex a Spatial operation: topological, euclidean, directional metric a sQL 3 allows user defined data types and operations Spatial data types and operations can be added to SQL3 a Open Geodata Interchange Standard (oGIs) Half a dozen spatial data types Several spatial operations Supported by major vendors, e.g. ESRI, Intergraph Oracle. IBM 2021/8/25
2021/8/25 15 Query Language for Spatial Database ◼ Extending SQL for Spatial Data ❑ Motivation ◼ SQL has simple atomic data-types, like integer, dates and string ◼ Not convenient for spatial data and queries ❑ Spatial data (e.g. polygons) is complex ❑ Spatial operation: topological, euclidean, directional, metric ❑ SQL 3 allows user defined data types and operations ◼ Spatial data types and operations can be added to SQL3 ❑ Open Geodata Interchange Standard (OGIS) ◼ Half a dozen spatial data types ◼ Several spatial operations ◼ Supported by major vendors, e.g. ESRI, Intergraph, Oracle, IBM