Details of Constraint Expressions
- Provide a way to create custom projections of
an arbitrary dataset. E.G.: If a dataset contains three variable
U, V and T a projections constraint can be
used to limit the data returned to only variable U.
- Provide a way to select data based on values.
An algebraic expression can be used to describe which values are to
be returned and which are not.
- Computed values may be returned instead of
values stored in the data set. For example, a given data set may not
contain the number of elements in a particular variable but the
length constraint expression function can be used to find
and return that value.
- Data servers can customize the set of functions
they provide. This allows servers to supplant the implementations
provided in the DODS core software and to provide special functions
which researchers may find useful but which are not part of the DODS