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RE: [xml-dev] RDF for unstructured databases, RDF for axiomatic

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 21 Nov 2002 18:38:36 -0600
Message-Id: <p05111b2bba03262f4752@[]>
To: "Brian McBride" <bwm@hplb.hpl.hp.com>, "Shelley Powers" <shelleyp@burningbird.net>
Cc: "Frank Manola" <fmanola@mitre.org>, "Jonathan Borden" <jonathan@openhealth.org>, <www-rdf-comments@w3.org>

>  >
>>  >Again -- you should say upfront, the purpose of this document
>>  and intended
>>  >audience -- it is not for a "general technical audience". It is for a
>>  >specialized audience, with specialized interests. And if people
>>  don't share
>>  >this specialized interest, or don't have the necessary
>>  background, you make
>>  >them feel inadequate and stupid. I'm not making this up -- I had
>>  someone who
>>  >is very smart and intelligent and well known in the industry say this.
>>  We certainly don't want to do that.
>>  Should we assume that a "general technical audience" has enough
>>  mathematics
>>  to be able to read the model theory document?  I guess it kinda
>>  depends on
>>  your definition of the term.
>>  Maybe rather than using such terms, you are suggesting there
>>  ought to be a
>>  (Oh, I can't resist the term, Pat please don't think this is pejorative)
>>  health warning on the model theory doc indicating what level of
>>  mathematical understanding it requires.  Maybe:
>>  [[
>>  This document culminates in a formal mathematical specification of the
>>  semantics of RDF and RDF Schema using a technique called model
>>  theory.  Its
>>  early sections include an introduction to the mathematics used
>>  later in the
>>  document.  These section are intended to make the document accessible to
>>  those who are comfortable with basic mathematical techniques such as set
>>  theory but have not met model theory before.  Some readers may prefer to
>>  read instead the concepts doc [@@] and the schema doc[@@] which cover the
>>  same material in less mathematical terms.
>>  ]]
>>  Out of interest Shelley, if you were to look at just at Appendix
>>  A - do you
>>  personally find that more approachable?
>If I'm not the targeted audience, Brian, it wouldn't matter whether I was
>more "comfortable" with this or not.
>If the semantics document is for the ontology group and as a discussion
>point for the RDF WG, it doesn't really matter if I'm comfortable with it,
>does it?
>>  >No document should ever make it's intended audience "feel stupid". If you
>>  >clarify the purpose of the semantics document, you can at least make a
>>  >person know that they don't need to understand this document, in order to
>>  >work with RDF. That this document is for the ontology working
>>  group and is a
>>  >RDF working group tool.
>>  You sound angry - do you mean to?  Would a health warning help?
>  > Is there a
>>  better way?
>Not angry. Not at all, though I did face on angry people last week trying to
>defend the RDF/XML.
>Health warning is about the worst thing you can do. "Excuse me, but you have
>to have college level math to understand this".
>But then, if you're like me and have spent the last 20 years creating
>applications rather than doing research, I may be a tad rusty with my
>college level math.
>No, what you should do put in what you told me:
>"This document was created to help the RDF WG understand the semantics....
>It should be viewable by a general technology audience with some experience
>in.... However, it isn't essential to work with RDF/XML or to understand the
>underlying RDF concepts. However, if you're .... you should make the effort
>to read and understand this document."
>Now, what is wrong with that?

Its not right, that's what. Brian said that we STARTED with the MT in 
order to help internal clarification, but even that was an 
overstatement. You have to understand that RDF isn't the first 
ontology language, though it is the first WEB ontology language. 
Ontologies have been deployed in industry now for about 20 years, and 
the roots of the game go back to the '60s, and are also the roots of 
logic programming, RDBs, and lots of AI-KR work. There is a mature 
technology and a very thoroughly worked out theoretical foundations. 
Among professionals in this field, not having a MT is like producing 
a programming language without a VM or an interpreter. The MT is the 
foundation on which all the rest is built, its absolutely essential. 
Without it, all is confusion: it is the oracle to which you bring all 
questions of validity, counterexamples, consistency testing. Its the 
foundation. So when addressing people who are likely to build RDF 
apps, an MT, or something of equivalent formality, is essential. And 
even our specs refer all questions of validity of inference to the 
MT; it really is central to RDF, its not just to help the WG 
understand the semantics; it *is* the semantics.

The moral for me being, I need to explain this stuff in a more 
accessible way. Sigh.


>  >
>>  Who has been saying what.  My take on this is (from a drafted
>>  suggestion to
>>  clarify this in schema)
>>  [[
>>  Three different kinds of container are defined. Whilst the formal
>>  semantics
>>  of all three classes of container are identical; they are ordered
>>  sequences, different classes may be used to indicate further
>>  information to
>>  a human reader. An rdf:Bag is used to indicate that the order of
>>  members of
>>  the container is not significant. An rdf:Seq is used to indicate that the
>>  order of the members of the container is significant. An rdf:Alt
>>  container
>>  is used to indicate that typical processing of the container will be to
>>  select one of the members.
>>  ]]
>Shelley puts gun to head and shoots self.

Right, that prose does rather need clarification. The key point is 
that RDF *describes* things. When it comes to containers, it 
*describes* containers. That is all it does. It doesn't construct, 
manipulate, implement or in any sensible sense 'provide' containers. 
It just lets you SAY what things are in your container and what type 
of container it is, and once you've said it, it undertakes to 
preserve that information for you and draw any conclusions it can 
manage to figure out from what you tell it. But RDF itself has no 
idea what a 'bag' really is, any more than it knows what, say, 
'humanBeing's really are. Unlike Java, it doesn't set out to actually 
build cleverly encoded bag-datastructures which can be manipulated 
and checked and modified. It just sits there and remembers what it 
was told. This is a thing called a 'bag' and it has this and this in 
it.... and this is a thing called an 'alt' and it has this and this 
in it. OK, got that. What's a bag? I dunno, but there's one called 
... and it has this in it and this in it... . Programming language 
VMs read code and construct huge edifices of process and data. RDF 
engines are more like librarians. There's nothing 'behind' the RDF, 
no machine state being referred to. Just like an RDB, in fact: the 
data *is* the RDB.

>>  is is very rough and needs tidying up but does that make sense to
>>  you?  Does that differ from what other folks are saying?
>>  >If you can't back something, and can't stay silent on same, then
>>  deprecate
>>  >it. However, if the majority of you feel that the construct is good, and
>>  >sound, and only a few of you don't like it, then document the
>>  disagreements,
>>  >but reassure the audience that the construct is not going away. Not only
>  > >will the construct be clearly defined, but the WG's opinions, and the W3C
>>  >official stand on same will be, also.
>>  >
>>  >Is this necessary for all specs? Not at all, but it sure seems
>>  to be needed
>>  >for this spec.
>>  >
>>  >The working group is delivering more than cleaned up and clarified
>>  >documents -- it's also providing a W3C official stand on how a
>>  specification
>>  >will be implemented and used. Any fudging on this will leave us worse off
>>  >than before.
>>  No there I must disagree with you.  We do not say anything about how to
>>  implement.  We define no processing model.  I agree with you it would be
>>  good to have one, but that is just one of the many things we have not
>>  done.  We define the syntax of the (ok 2) language, we provide a
>>  specification of the semantics of the language and a guide on how
>>  to write
>>  the things you want to say in it.  But that is all we do.  And it has
>>  bl**dy well exhausted me working with these guys to get that far.
>And I know you all have worked your butts off here (can I say 'butt' in a
>W3C mailing list?)

You would be amazed.

>  I respect that. But I'm literally between a rock and a
>hard place -- between the average Joe wanting to use RDF for a door factory
>in Wisconsin, and those in white coats who see RDF as the cornerstone for
>some grand, esoteric semantic web.

The great and terrible thing is, the grand, esoteric SW is going to 
be made of average Joes if it is going to happen at all. So its all 
up to you, Shelley :-)

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Received on Thursday, 21 November 2002 19:38:46 UTC

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