Re: Meaning of Alt

At 12:01 PM 9/7/00 -0700, Ray Fergerson wrote:
>Graham Klyne wrote:
> > (b) the lack of clarify about what rdf:Alt means, and the lack of a
> > compelling prototypical application for it suggests to me that it might be
> > struck from the core specification.
>
>I'd actually prefer to keep it but just remove the implication that
>the items are "the same" in some unspecified way.  It would then map
>cleanly to the common programming language "enumerated type" concept
>which has lots of uses.  Enumerated types can also modeled as
>subclasses or instances but sometimes it is just more natural to put
>some things in a bag and say "pick one". Something like the colors on
>a stop light can reasonably be modeled in this way rather than
>introducing a totally artificial "stop_light_color" class.

Hmmm... I think this is in danger of conflating union types with 
alternative values.

(An enumeration type can be viewed as a union type of its individual 
enumerated values)

If this is being used in the context of a type definition schema, then your 
comments make sense.  But it seems to me that the primary use of rdf:Alt 
would in the _value_ of some _instance_ of a type, so the issue of 
enumeration does not arise -- it's just a value.

#g

------------
Graham Klyne
(GK@ACM.ORG)