A deductive object - oriented approach to Geographic Information Systems
2.3 Class BaseMapObject
This GIS extensional database is composed of a set of basemap objects. A basemap object is an instance of class BaseMapObject.
[ Definition 3.5] An attribute object is the aggregation of attribute name and a Primitive or GeoObject Object. The attribute object is represented by the form
(0) where L is an object of type STRING and o is a Primitive or GeoObject object.
Examples of attribute objects are
Id ( 'Dusit')
Pt ( 1 @ 2 )
Grade (1)
[Definition 3.6] A spatial object is an object of classes Point, Line or Polygon, or existing subclasses of these classes. A spatial object is the aggregation of a1, a2, …, am and b1, b2, … bn inherited from a super class of the spatial object and bj an Attribute object of its own class.
A spatial object is represented as s (a1, a2, am, bi, b2, bn) where s is an object of type STRING representing the class name. An example of this class of objects, i.e. Hotel object, is
Hotel (id ('Dusit'), pt (a @ 2), no of Floor (10) style ('Roman'), year Built ( 1965),no Room (500), grade (1))
[Definitions 3.7] A basemap object is the aggregation of a mapid object and spatial objects. A mapid object is an instance of class STRING. A Spatial object is an instance of class Geo Object. A basemap object is represented by a set of clauses mapid (s) where s is a spatial object.
No of Floor (10), Style ('Roman'), year Built1965), no Room (500), grade (1) )
3 The GIS Intensional Database
The GIS intensional database employs the idea from the first order predicate logic where terms are defined as follows.
- a variable is a term.
- a primitive object is a term.
- an attribute object is a term.
- a spatial object is a term.
The GIS intensional database consists of a set of derived map objects. A derived map object represents a thematic map. the derived map object is represented by the form:
m (s) - m1 (s1), … , mn (sn), p1 (arg1),…, p, (arg),
Where m
i is the map identifier, S
j is the spatial object associated with map m, p
i is the GIS built-in predicate, and arg1 is the argument required by p
i.
The declarative semantics of the rule above is "if m, (s
1) and. .. mn (s
n) and P1 (arg1)… and p, (arg,) are true then m(s) is true.
4 The GIS Date Definition Language
There are five data definition language commands. Their BNF definitions are as follows:
