#140: Clarifying the role of attributes on boundary variables.
-----------------------------+------------------------------------------
Reporter: davidhassell | Owner: cf-conventions@…
Type: enhancement | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords: boundary variable, attribute
-----------------------------+------------------------------------------
Comment (by davidhassell):
Hello Karl, Jonathan,
Allowing the term values which span the vertical dimension to ''not'' have
a `bounds` attribute would certainly make writing software harder, as the
software would have to work out that a formula terms named variable is
associated with a boundary variable and then make that connection
explicit.
Running with Jonathan's idea of insisting that the boundary variable has a
`formula_terms` attribute, I would take it further and insist that term
values which span the vertical dimension ''must'' have a `bounds`
attribute which points to the appropriate variable named in the boundary
variable's `formula_terms` for its boundary variable. This is also a
backwards-incompatible change:
If a parametric coordinate variable with a formula_terms attribute
(ref section 4.3.2) also has a bounds attribute, its boundary variable
must have a `formula_terms` attribute too. Because the same standard_name
must describe both variables, the formula must have the same terms (as
specified in Appendix D), but a different variable must be named by the
two `formula_terms` attributes for any term which depends on the vertical
dimension, because the boundary variables have one more dimension. For
these terms, the boundary variable's `formula_terms` must name the bounds
of the variables named by the vertical coordinate variable's
`formula_terms`.
That said, I like to think that we can find some non-confusing wording
which allows my case 1, and so no backward-incompatible changes would be
necessary.
All the best,
David
--
Ticket URL: <https://cf-trac.llnl.gov/trac/ticket/140#comment:8>
CF Metadata <http://cf-convention.github.io/>
CF Metadata
