# Re: Urgent! Semantic question about rdfs:domain.

From: Dan Connolly ([email protected])
Date: 04/24/01

```pat hayes wrote:
>
> [...]
> It says
>
> <rdfs:domain,?P,?C>    means:    if <x,y> in IR(?P) then x in IC(?C)
>
> but if the above is correct then it ought to say:
>
> <rdfs:domain,?P,?C>    means:   if x in IC(?C) then for some y, <x,y> in IR(?P)

Er... yeah, the latter corresponds to what I remember
from when I first learned about functions, domains,
and ranges. But the former is the rule that I've used
several times recently.

The latter does imply the former, no?
(I can't seem to work out the details in my head.)

> If the semantics is correct, however, then the example in the
> walkthrough is rather misleading, and we will need to correct against
> any potential misunderstanding. Also, in this case, HOW does someone
> give a 'lower' bound to the domain of a property? Eg how can one say
> that hasParent applies to *any* animal? (If both domain and range
> restrict from above, then it would be consistent to give all
> properties empty domains and ranges.)

Er... huh? an empty range for ?P means there are no ?y's
for which <?x, ?y> in ?P, no?

I think I'm lost.

> I await clarification from the Semantic Gurus, and will write
> appropriate prose for the walkthru when clarity is restored to my
> mind.

I'm no semantic Guru, but I find the latter definition
more appealing.

> Pat Hayes
>
> PS. A related question. If
>     <rdfs:domain,?P,?D>
>     <rdfs:range,?P,?R>
>     <inverseOf,?P,?S>
>     <rdfs:domain, ?S,?R>
>     <rdfs:range,?S,?D>
> ??

No, I don't think so... but I can't think of a counter-example
just now.

> PPS. The only way to really learn something is to try teaching it to
> other people :-)

Quite.

--
Dan Connolly, W3C http://www.w3.org/People/Connolly/
office: tel:+1-913-491-0501
pager: mailto:[email protected]
(put return phone number in from/subject)
```

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