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Re: ACTION 2001-08-24#9 : issues with containers

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 30 Aug 2001 13:13:49 -0700
Message-Id: <v0421010eb7b4477c984d@[130.107.66.237]>
To: fmanola@mitre.org
Cc: w3c-rdfcore-wg@w3.org
>All--
>
>I think I need some clarification on this subject (said need is *not*
>due to any lack of clarity in Pat's summary;  these issues have been
>fuzzy to me for some time).  Unfortunately, most of the discussion I
>remember was couched in terms of the "whether there can be gaps in the
>property sequence" issue, and I have trouble translating that decision
>into a clear decision on the matter of partial vs. complete
>descriptions.  In particular, I need a clearer understanding of what is
>meant by saying (or not saying) that a set of container contents is
>*all* that is in a container (e.g. "all as far as I'm concerned" vs.
>"all anywhere in the Universe").  Here's my "understanding" (to use the
>term loosely) of the situation, (mostly) independently of how we label
>the container members:
>
>1)  In general, a (perhaps *the*) basic reason we say we can't constrain
>the members of containers is that "anyone can say anything about
>anything".  That means that if a container is specified in some
>collection of RDF, someone somewhere else might assert that there are
>additional items in the collection.  Right?

Not quite. The 'ACSAA' principle doesnt actually prevent one saying 
that a container has exactly these things and no more; but it does 
mean that if you are allowed to say that, then something someone else 
might say could contradict what you say. It raises the possibility of 
disagreement. So it can be said to be in opposition to a rather 
stronger principle, which might be characterised as 'anyone can say 
anything about anything and nobody will ever disagree with them'. 
Much of RDF seems to be designed on the ACSAANED principle rather 
than the ACSAA, however, so maybe this is indeed the reason for it. 
Right now much of the simplicity of RDF can be attributed to the fact 
that it is impossible to express an inconsistency in it, hence 
impossible to actually disagree with anything. I think that ACSAANED 
isn't a feasible basis for communication between agents, human or 
machine, but it certainly does reflect a happy 'love one another' 
picture of the world (one that reminds me rather of the early 60s, in 
fact.)

>2)  However, in the specific examples used in Sections 3.1 and 3.2, the
>containers are all anonymous.

Good point, although I think that the 'anyone' in ACSAA/NED includes 
oneself, so that it is always considered kosher to add some more 
information yourself, and presumably you could do that even if the 
node was anonymous.

>So, e.g., in Figure 4 (p95), the model
>that defines the container says that the container has 5 members.  How
>can anyone else assert that there are additional members, since the
>container is anonymous?  Even if there were a gap in the sequence of
>property sequence items, if the container is anonymous, how could you
>assume there were any additional members?

More to the point, how could you know there were not? Part of the 
basic game of giving *descriptions* is that the interpretation is 
required to satisfy them, but not to satisfy them *exactly* (unless 
they are so expect that only one interpretation is possible). If I 
say three things exist, I do not thereby say that a fourth one does 
not exist. Often in ordinary conversation things like this are 
assumed, but the 'rules' by which those assumptions are made have to 
do with human conversational practice (what Grice calls 
'conversational maxims', eg don't give irrelevant information, always 
give all relevant information, and so on) rather than strict 
assertional content.

>
>3)  Suppose that the containers are assigned actual URIs, and so even
>though I may define a container with 5 members, someone else could
>assert the existence of additional members.  I hope, even in that case,
>that we're assuming that there is some way to distinguish the members I
>asserted from the ones asserted by someone somewhere else (and possibly
>also to identify who created the container in the first place)?

Not in RDF there isn't.

> That
>is, if I assert that I have two children, while it may be possible for
>someone else to say that I in fact have one additional child, normally
>my assertion would be taken as that of a "closed" (having only the
>members I specified) set *as far as I'm concerned*.

Again, I think that this is very debateable. If you were to use the 
actual words "I have two children" in a conversation, then indeed 
Grice's rules would suggest that you mean that you have precisely two 
kids, since to use the precise number in that context would be 
misleading if you in fact had three, and could have said 'three' just 
as easily.  But that is a very fragile assumption, and depends on the 
conversational context. Suppose for example that you were visiting 
your kid's school and told someone, pointing to the kids in question, 
"Those are my children", then that would be quite consistent with 
your also having other children, even though the same information is 
being asserted. Or suppose you were to say in a conversation about 
books, "I have read all of Shakespeare's sonnets"; it wouldn't be 
reasonable to infer that you hadn't read anything else.

> Perhaps that
>ability to distinguish who said what is all we need;  Frank said the
>members are a, b, c;  Joe said the members are x, y, z.  The receiver
>gets to decide who the members really are.

I think it runs deeper than that.

>4)  On the other hand, we might want to explicitly say whether, when I
>defined the container, I *intended* the container to be "closed" (having
>only the members I specified) or "open" (having possibly other
>members).  Note that even if my intention was for the container to be
>closed, that may not (and it probably won't) prevent others from
>asserting additional members (maybe I was wrong);  but it is an
>expression of my intent, and would at least indicate (if any more
>indication was necessary) that I'm not responsible for those other
>members.

Right. It would allow you to say something that others could disagree 
with, but at least conveys your intended meaning. Right now you can't 
even say it.

>
>5)  It seems to me that if "anyone can say anything about anything", and
>we interpret this to allow anyone to add additional members to
>containers I define which I intended to consider "closed", there ought
>to also be a way for me to express that "closed" intent;  otherwise,
>there's something I can't say about my own container!

Quite.

Pat

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Received on Thursday, 30 August 2001 16:12:41 EDT

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