[db-wg] AS-NULL

Nigel Titley wrote:
> 
> On 15/12/14 16:26, Nick Hilliard wrote:
> 
>> 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.
>>
> I don't see any particular problem with the NCC creating and owning such
> an empty set

Same here, in principle, but...

After having a look at some RFCs I'd suggest to rather go for an AS-EMPTY,
as the use of AS0 (AS zero or null) seems to have some semantics attached.

I may easily be wrong. :-)

Wilfried

> Nigel