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Spatial SQL: A Query and Presentation Language. Max J. Egenhofer (Presenter: Yi-Shin Chen). Outline. Introduction Spatial query language Guidelines for an SQL Extension Requirements for Spatial Query Languages Separating retrieval and display instructions Spatial SQL - PowerPoint PPT Presentation
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Outline
Introduction Spatial query language
Guidelines for an SQL Extension Requirements for Spatial Query Languages
Separating retrieval and display instructions Spatial SQL
Spatial domain, operations, data definition, selecting by pointing
GPL Display Mode, variables, scale, window, context, content
Conclusion
Introduction
The need for spatial query language Geographic Information System (GIS), Image Database,
Remote Sensing
Existing query languages are insufficient Only address the particular properties of lexical data
Treat spatial data as integers and strings
Spatial Data have additional properties Geometry
Graphical presentation
Example
SELECT ImageNameFROM S_ImagesWHERE RECTANGLE(-77.748125, 38.695 , -77.348125 , 39.095) OVERLAPS area
image4/W775647N389000.jpgimage4/W775644N388927.jpgimage4/W775644N388855.jpgimage4/W775641N388783.jpgimage4/W775555N389000.jpgimage4/W775552N388927.jpgimage4/W775550N388855.jpgimage4/W775547N388783.jpgimage4/W775463N389002.jpgimage4/W775461N388930.jpgimage4/W775458N388858.jpgimage4/W775455N388786.jpg
Query Result :
Introduction -II
Extending an existing language with spatial concepts
Reason: spatial databases contain both spatial and non-spatial data that will be the subject of user queries
SQL + Spatial Concepts = Spatial SQL
Guidelines for an SQL Extension
SELECT-FROM-WHERE clause should keep Three categories of queries
Exclusively about spatial properties About non-spatial properties Combine spatial and non-spatial properties
Should allow the user to pose non-spatial queries appropriately
SELECT-FROM-WHERE is already complex enough to use
Requirements for Spatial Query Languages
GEOQL Extended SQL
PSQL KGIS TIGRIS
Spatial ADT + + + + +
Graphical Presentation + + + + +
Result Combination +
Display of context + +
Content Examination
Selection by Pointing + +
Display manipulation +
Legend
Labels +
Selection of Map Scale +
Area of Interest +
Separating Retrieval and Display Instructions
User expectations Pose several queries in a raw Only modify the graphical parameter of objects
Integration of a full display description into the query language would make each user query unnecessarily complex and long
Retrieval language -> Spatial SQL Presentation language -> GPL
Spatial Domain
Provides a higher level abstraction of data
Four spatial domains: Spatial_0, Spatial_1, Spatial_2, Spatial_3
Spatial relationships refer to spatial concepts
such as topology and metric
Only the specified spatial operations and
relationships apply to spatial attributes
Spatial Data Definition
In general, a spatial relation will have exactly one spatial attributeCREATE TABLE city
(name char(100)
geometry spatial_2);
Spatial SQL does not prevent from defining several spatial attributes for a objectCREATE TABLE ocean
(name char(100)
geometry spatial_2
generalized_geometry spatial_0);
Spatial Operations – part one
Functions upon a spatial attribute Dimension, boundary, interior, bounding-Nodes,
bounding-Edges, interior-Nodes, interior-AreasSELECT boundary (geometry)
FROM city
WHERE name = “Los Angeles”
Deal with arithmetic operations Length, area, volume, perimeter, extreme coordinates,
complement, convex hullSELECT area (geometry)
FROM city
WHERE name = “Los Angeles”
Spatial Operations – part two
Binary spatial operations Distance, direction, angle, minimum, average Prefix formulation [Distance(city.geometry, highway.geometry)]
SELECT city.name FROM city, oceanWHERE distance (city.geometry, ocean.geometry) < 100KM
Binary topologies relationships Disjoint, meet, overlap, covers, inside, contains, equal,
left/right, north/south, over/underSELECT city.name FROM city, oceanWHERE city.geometry MEET ocean.geometry
Selection by Pointing
Interactive communication with drawing is enabled with the PICK qualifier which allows users to formulate queries.
SELECT name
FROM city
WHERE geometry=PICK
Ambiguities in the selection may exist User will be offered the possible choices and then
asked to identify the target
GPL
The concept of the display environment The query result is rendered according the
display description Offers instructions to SET or CANCEL a
graphic specification (can be qualified with PERMANENT)SET MODE highlight
With IMMEDIATELY to update the current display prior to asking the next querySET IMMEDIATELY COLOR red
Display Mode
Six display mode Conventional alphanumeric display NEW: starting a new drawing ex. SET MODE new; OVERLAY: adding the result onto a existing drawing REMOVE: erasing the result from a drawing INTERSECT: determining the common objects on the
display and in the query result HIGHLIGHT: emphasizing the result
Non-spatial attributes in the SELECT clause will be represented as label
Visual Variables
Graphic attributes can be specified for either an entire spatial relation or instances of spatial relationsSET LEGEND
COLOR black
PATTERN dashed User can check the current setting by “looking
at the legend” This part of GPL depends upon the user’s
hardware
Scale and Window
The scale of the graphical presentation can be described with the command SET SCALESET SCALE n (representing a scale factor of 1:n)
The window describing the area to be displayed can be described with SET WINDOW
The window can be determined by two pairs of coordinates the minimal bounding rectangle from the result
SET WINDOWSELECT geometryFROM roadWHERE town.name = “Orono”;
Context
The interpretation of graphical presentation is extremely depend on the context and environment
GPL allows the user to define spatial relation with SET CONTEXT as graphical context which is during query processing merged with the actual user query
SET CONTEXTFOR road.geometry
SELECT building.geometry, road.name
FROM road.parcel, building;
Content
A needed control mechanism with which user
may examine the content of a drawing
The content is the logical combination of
queries the result of which were combined
with OVERLAY and REMOVE
Content is only observable (cannot SET or
MODIFY)
SHOW Content
Conclusion
Spatial SQL +GPL
Spatial ADT +
Graphical Presentation +
Result Combination +
Display of context +
Content Examination +
Selection by Pointing +
Display manipulation +
Legend +
Labels +
Selection of Map Scale +
Area of Interest +
Appendix
Conventional Spatial Database Geodetic DataBlade Module
http://examples.informix.com/frameset.html#top?initial_page=/doc/case_studies/datablade/geo/geoLOC.html
NCR Teradata Object Relational Database (TOR) Oracle Spatial ESRI Spatial Database Engine (SDE)
systems like Oracle, Microsoft SQL Server, Sybase, IBM DB2, and Informix