7.8.4
Coordinate reference system handling
In filter expressions, geometric values shall be encoded using GML, as given in ISO 19136. In GML, the optional srsName attribute is used to specify the coordinate reference system for the coordinates of geometry. Attention is drawn to the fact that specifications that reference this International Standard shall specify how to handle the following cases that can arise where two expressions that resolve to geometric values are compared:
a)
the two geometry values have difference srsName values;
b)
one or both of the geometry values do not have an srsName value specified.
Although this International Standard does not mandate what actions to take to resolve these situations, it is clear that some strategies for resolving these issues can require coordinate transformations to be applied to one or both of the geometries.
7.9
Temporal operators
7.9.1
General considerations
A temporal operator (see Figure 7) determines whether its time arguments satisfy the stated temporal relationship. The operator evaluates to true if the temporal relationship is satisfied. Otherwise, the operator evaluates to false.