For most operations
that involve the spatial database, you refer to composites of the
spatial data variables rather than directly to the variables in the
spatial data sets. A composite consists of the following elements:
-
a variable association that identifies which variable
or variables in the spatial database comprise the association. The
variable association can specify a single variable, or a pair of variables
that define a bilateral (left-right) association. The association
can also specify two pairs of variables that define the start and
end of a directional (from-to) bilateral association.
-
a class attribute that identifies the role of the composite
in the spatial database.
For example, the chains
data set can have a variable that is named FEANAME that contains feature
names. You can create a composite for the FEANAME variable. The composite
assigns the class attribute NAME to indicate that it represents feature
names. In another example, the chains data set has COUNTYL and COUNTYR
variables that contain the codes for the counties on the left and
right sides of the chains. You can create a composite that is named
COUNTY. The composite identifies the bilateral relationship between
these two variables. The composite assigns the class attribute AREA
to indicate that it defines county areas in the spatial data.
Composites are created and modified using the COMPOSITE
statement in the GIS procedure. Composite definitions are stored in
the spatial entry.
See COMPOSITE Statement for more information
about using the GIS procedure to create or modify composites.