W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > March 2003

Re: Social meaning discussion 6th March

From: Graham Klyne <GK@NineByNine.org>
Date: Tue, 04 Mar 2003 15:14:39 +0000
Message-Id: <5.1.0.14.2.20030304145335.038658d0@127.0.0.1>
To: pat hayes <phayes@ai.uwf.edu>
Cc: Tim Berners-Lee <timbl@w3.org>, Dan Brickley <danbri@w3.org>, Brian McBride <bwm@hplb.hpl.hp.com>, pat hayes <phayes@ai.uwf.edu>, Bijan Parsia <bparsia@isis.unc.edu>, RDF Core <w3c-rdfcore-wg@w3.org>

At 10:31 PM 3/1/03 -0700, pat hayes wrote:
>>  Something has one meaning.
>
>This isn't true even in ordinary human discourse in natural language. 
>There just is no such notion of a single 'one meaning'; the idea isn't 
>coherent.

Pat,

I'd like to explore this a little, noting that RDF is not "ordinary human 
discourse in natural language".

Stepping back from meaning that can be formally specified, I'd like to try 
a notion of a single meaning (in RDF):
(a) each URI used has exactly one denotation
(b) each URI used as a property has just one relational extension

(A consequence --for which this is sufficient but not necessary-- would be 
that the truth or falsity of any expression using a given vocabulary of 
URIs is fixed.)

I'm not attempting to describe a specific interpretation in the model 
theoretic sense.  Though I suspect that there can be only one such 
interpretation (on a given vocabulary) that could concur with such a meaning.

We have no way of fully specifying such a "one meaning", but I think it's 
reasonable to allow that we can develop successive approximations that 
converge (asymptotically, as it were) to such a meaning.

This may not be a useful idea, but I'm trying here to see if there may be 
ways to reconcile what I think are two apparently-reasonable viewpoints.

#g
--

At 10:31 PM 3/1/03 -0700, pat hayes wrote:
>>Jeremy Carroll wrote:
>>
>>>
>>>tbl:
>>>
>>>>>>2. The meaning of the statement is defined by the definition
>>>>>>of the predicate, as applying to the subject and object identified by the
>>>>>>definition of the subject and object terms.
>>>
>>>Danbri:
>>>
>>>>>This for me is the crux: do we mean the machine oriented 'definition'
>>>>>in RDFS or OWL or N3, or some more rounded/scruffy/social notion of 
>>>>>definition.
>>>
>>>
>>>I find Bijan's observation compelling
>>>[[
>>>But there's no vague, much less precise, definition of "defining 
>>>information". And I'm a logical reasoner, will this information be 
>>>opaque to me? (Well, if in German, yes, but *all* human reasoners?)
>>>[...]
>>>So it's formal meaning isn't fixed IN ANY WAY by the "authority"? And 
>>>the social meaning?
>>>]]
>>
>>
>>There seem to be a confusion here that things have two meanings, a 
>>"formal" one
>>and a "social" one.    I don't think that is useful.
>
>I think it is essential, although this way of putting it is potentially 
>confusing. It might be better to distinguish between how much of the 
>meaning is accessible to who and to what. The 'formal' meaning is that 
>part which is accessible to software. But even the 'social' part, ie all 
>the rest, varies from reader to reader. In some cases, a reader might find 
>more meaning than the original writer thought was in the document.
>
>>  Something has one meaning.
>
>This isn't true even in ordinary human discourse in natural language. 
>There just is no such notion of a single 'one meaning'; the idea isn't 
>coherent.
>
>>"inverseProperty" can be defined mathemaically, but remember that  the
>>mathematical symbols used are probably defined in english somewhere.
>
>That is highly debateable and depends what you mean by 'defined', but in 
>any case its irrelevant to the issue here. If your point is that *all* 
>meanings are ultimately described in English, that isn't true.
>
>>"color" can't be defined formally in terms of mathemaics, unless you have
>>assume a lot of other terms to do with spectral reflectivity and light.
>
>Well, "color" actually can be defined in scientific terms, in fact, but 
>you'd be better with an example like "red" which probably can't be defined 
>at all. This has got nothing whatever to do with mathematics, but it does 
>tend to show that there isn't any single meaning to words like color names.
>
>>>
>>>Two points:
>>>- "whatevers available" is simply not clear enough.
>>
>>There are a lot of social systems for relating definitoins to terms.
>>These include domain name owndership, the Web, etc.
>>The web is a big place.  Predciates and terms vary enormously.
>>For RDF to be able to describe real things, it is essential that
>>some terms be defined in english.
>
>Why English? And why is this true? You can't define "red" in English. And 
>more to the point, maybe, what does 'defined' mean here? RDF can't use 
>definitions given in English.
>
>>  Look at the cyc ontology.
>
>That is a very bad example for your point: the intended purpose of Cyc is 
>precisely NOT to rely on English definitions.  The meaning of any CYC term 
>is completely defined by the CYC axioms using that term (and all linked 
>axioms, ie ultimately by the whole of Cyc.)  You can strip out all the 
>English comments and the meaning is unchanged. The same goes for almost 
>all large-scale ontology work, in fact.
>
>>I'm not sure what you are unhappy with, here.
>>Are you saying it is not clear enough?
>
>It certainly is not clear enough.
>
>>Are you saying that
>>it is not clear what the definitions of the terms are?
>
>It is clear that any English definitions cannot be reflected in any 
>normative account of meaning which is reflected in any operation of any 
>RDF software. IF RDF tries to incorporate any such notion of meaning into 
>its spec, then it has just become a joke.
>
>>Are you saying that the english definitions should not be allowed?
>
>Allowed in what sense? What I am saying is that allowed or not, they are 
>not the slightest actual USE. Any sense of 'meaning' which depends on them 
>isn't going to influence in any way what any piece of software does to the 
>RDF. And since the point of the spec is largely to help writers of 
>software, referring to something that is necessarily irrelevant is either 
>pointless or actively harmful.
>
>>Or do you want a clean algorithm for determining which
>>english documents define a given term, from the web?  (That we could probably
>>arrange.)
>
>That would be very interesting. I doubt if this can even be made precise 
>enough to be meaningful, let alone provided as an algorithm. And in any 
>case, suppose you could. Now, how is my RDF engine going to read and 
>understand those English documents?
>
>>>
>>>- RDF has decided to avoid the notion of definition for the formal 
>>>semantics, we shouldn't then have it in the informal semantics.
>>
>>Well, every specification upon  which the web has depended up till now, 
>>including
>>Ethernet and unicode and TCP/IP and HTTP has had the meaning of its terms
>>and structures explained in english, informally.  These specs have been used
>>to build software, resolve many discussions,  and so on.
>
>Yes, but this reply misses an essential point. The part of those specs 
>whose meaning is fixed between software apps is the part that can be 
>specified in the specs. None of those specs have set out to define a 
>general meaning-carrying representation. In the case of ontology languages 
>like RDF, the common part that can be defined by the spec is the *general 
>rules* for meanings, ie the semantics, NOT the 'meaning' of particular RDF 
>URIrefs. The spec says nothing at all about what <ex:myUri> 'means', and 
>if you write a document in English explaining what its supposed to mean, 
>then its not the slightest use or relevance, since no piece of software on 
>the planet in the forseeable future is going to be able to read your 
>English 'definition'.
>
>>  There are a mass of
>>RDF schemas and related documents going to be written -- but it needs the RDF
>>spec to pass on the authority to them to define their fields.
>
>I don't see how the spec of a language can, or should, pass on any 
>authority to define anything. It didnt have the authority to define the 
>meanings of any items not in its namespace in the first place. What it can 
>do, and does, it specify how to characterize the content of any piece of 
>the language, so that definers of meanings can determine how to constrain 
>those meanings using the language. That is what the model theory sets out 
>to do.
>
>>Just because *some* aspects of the meaning of *some* RDF terms can
>>be expressed formally
>
>THOSE ARE THE ONLY ASPECTS OF MEANING DEFINED BY THE SPEC. If you want the 
>spec to define other aspects of meaning, please tell us how to write it 
>(the spec) so as to refer to those other aspects of meaning. Its not good 
>just using words like "meaning" and "definition" without saying what we 
>mean by them. Words like this don't have exact enough meanings to use in a 
>specification.
>
>>   does not remove the duty of the RDF spec to
>>say what an RDF document means.
>
>The SPEC cannot possibly say what a particular RDF document means, any 
>more than a dictionary can tell a story. It can only give general rules 
>for attaching meanings to documents, which is what the semantics does.
>
>>The formal semantics cannot define "color".
>
>Right, and "color" can't be defined in RDF.
>
>>Suppose I send you an RDF document syaing (in n3)
>>
>><http://example.info/ips/gg5#y004> <http://example.com/dsaf#enFap> "176".
>>
>>How would you know what I was telling you?
>
>I would know that some thing had some property with value '176' (a 
>string), and if that's all the RDF I can see, that is ALL I know. If you 
>want me to know more, you had better send me some more RDF.
>
>>How would someone who had not heard of RDF before?
>>The mime type would take them to the RDF spec and -- then what?
>
>The above is what I would learn from the RDF spec. Of course the RDF spec 
>can't tell me what you mean by <http://example.info/ips/gg5#y004>; and you 
>might tell ME what you mean in English, but (this being the semantic web) 
>that's largely irrelevant; the question at issue is what some piece of 
>software acting on my behalf can get out of it. If its written in English, 
>the answer is, nothing.
>
>>>For me, either of these is fatal. This cat has had its nine lives.
>>
>>Fatal for the idea of defining what an RDF document means?
>>How sad.
>>In that case, I suppose we had better start all over again, as
>>we have ended up with a languge of meaningless documents.
>
>You can start over all you want, but you will not get anything much better 
>than this (except in the sense that OWL is better than RDF, and full FOL 
>would be better than OWL). To get better than this you will need to create 
>a web of movie-style Artifical Intelligences, and you won't get that done 
>by a W3C working group. All languages - even human languages like English 
>- are 'meaningless' in some very strict sense. Their meaning is what a 
>cognitive agent can get out of them, and RDF agents - in fact, any 
>software agents that we know how to build -  have pretty limited cognitive 
>powers.
>
>>If  RDF is only be to be used to encode mathmeatical
>>formalisms,  and not information about the real world,
>>do we need another langauge to express data?
>
>This discussion has nothing to do with mathematics versus the real world. 
>Model theory is about worlds, including the real world. The point at issue 
>is HOW MUCH INFORMATION is encoded in some RDF; and the answer is, rather 
>little. But we knew that up front, before we started. It is obvious that 
>RDF cannot encode the kind of information that humans can send to one 
>another using languages like English, in a form useable by software 
>agents. But that's not a failure of RDF: *nothing* can do this. To do this 
>would require us to be able to provide software with human-level cognitive 
>powers.
>
>Pat Hayes
>--
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-------------------
Graham Klyne
<GK@NineByNine.org>
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Tuesday, 4 March 2003 10:21:28 EST

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