[db-wg] AS-NULL

On 15/12/2014 16:13, Job Snijders wrote:
> Can you elaborate on the use of AS-NULL? Isn't it common place to use
> something like "NOT ANY"?

"NOT ANY" is not the same as AS-NULL - they're not interchangeable.

AS-NULL is a convenience placeholder token for where might be a need to
have an empty as-set.  My particular itch today involved needing to use an
AS-SET of some form, but where the contents didn't particularly matter.  It
was more convenient to use an empty set rather than a set with some members
in it because that gave an element of semantic consistency.

There are other similar sets in the various irrdbs, e.g. AS-EMPTY occurs in
RADB.  This suggests that there is at least one other person in the world
who needs this sort of construct.

Nick