SPATIAL DATABASES

Many operations can be defined for different spatial data types.

ext={lines, regions}, geo={points, lines, regions}

• Spatial predicates for topological relationships:
  
  • inside: geo x region → bool
    
  • intersect, meets: ext x ext → bool
    
  • adjacent, encloses: region x region → bool
    
• Operations returning atomic spatial data types:
  
  • intersection: line x line → points
    
  • intersection: region x region → region
    
  • plus, minus: geo x geo →geo
    
  • contour: region → line
    
• Spatial operators returning numbers
  
  • dist: geo x geo → real
    
  • perimeter, area: x region → real
    
• Spatial operations on set of objects
  
  • sum: set(region) x region→ region
    It is a spatial aggregate function, geometric union of all attribute values, e.g., the union of a set of provinces determines the area of the country
    
  • closest: set(geo) x geo → set(geo)
    It determines objects whose geometries have minimal distance from a spatial query object
    
  • Other complex operations: overlay, buffering, …
    

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