W3C home > Mailing lists > Public > public-awwsw@w3.org > March 2011

Re: please review issue-57 document draft before Tuesday telcon

From: Jonathan Rees <jar@creativecommons.org>
Date: Fri, 18 Mar 2011 12:59:05 -0400
Message-ID: <AANLkTimsgUgPKKCSkdESXQAVcc2_tQHLrBOjPk2EP-J0@mail.gmail.com>
To: David Booth <david@dbooth.org>
Cc: nathan@webr3.org, AWWSW TF <public-awwsw@w3.org>
On Fri, Mar 18, 2011 at 12:06 PM, David Booth <david@dbooth.org> wrote:
> On Wed, 2011-03-16 at 07:52 -0400, Jonathan Rees wrote:
>> I guess my question is: Under "take it at face value," many URIs are
>> supposed to be taken to refer to WS(u). So, under what set of
>> circumstances, if any, will an automaton be able to detect that URI is
>> supposed to refer to IR(u)?
>
> I like the way you're putting this -- that the criterion is to enable an
> automaton to make the detection -- but I think the way you've stated it
> reflects too strong an RDF bias.  The vast majority of URIs on the web
> -- easily 99%+ -- arguably refer to IR(u), not WS(u), so I think it
> would make more sense to state the goal with the opposite default:
> [[
> Under "take it at face value," many URIs are
> supposed to be taken to refer to IR(u).

You're talking not about "take it at face value" but about some hybrid
approach in which some u refer to IR(u) and some don't.  Pure "face
value" would mean read the document and see what it says about its own
URI. If it says nothing about its own URI, you know nothing. That's
not the same as knowing that u is meant to refer to IR(u) in some
(most) cases.

Maybe I wasn't clear - or maybe I ought to redefine what "face value"
means in the report - but then the sometimes-IR(u) sometimes-WS(u)
case is really quite different always-WS(u), no matter how the
partition is calculated.

> So, under what set of
> circumstances, if any, will an automaton be able to detect that URI u is
> supposed to refer to WS(u)?
> ]]

My point is that the introduction of "face value" for *any*
derefenceable URIs creates FUD around *all* dereferenceable URIs.
That's why I'd prefer to say that IR(u) is the exception to a WS(u)
default rule. Another reason to put it this way is because proponents
of "face value" have pretty much put it this way by saying "we don't
need no metadata". That is, to them, the IR(u) case never happens in
situations of importance to LD. (This must mean that @href is not
referential; and I would be willing to give that to them, not because
I like it but because it's a completely defensible position.)

In the end I don't think it matters much, but I'll consider whether
flipping it works better, or doing something more symmetric. I guess
there are three cases: all robots can detect IR(u), all robots can
detect WS(u), and gray area where some can tell them apart, and some
can't.

> But I think the bigger problem occurs if you implicitly assume that
> IR(u) is not the same as WS(u).

If I ever assume that, even implicitly, then there is a mistake in the
report. Please give me specific instances. My guess is that you are
drawing invalid conclusions; but so would others, and they have to be
averted early.

You can always establish that IR(u) = WS(u) just by making the content
be the statement <u> :accessibleVia "u".

> In other words, the definition of :IR
> MUST NOT say that it is disjoint with anything.

I never say this. All I say is that most IR(u)'s will make good
metadata subjects and so metadata statements will be true of them. Let
people make of this what they will.

Will try to clarify.

>  (And lest anyone
> complain that if :IR is not disjoint with anything, then we have said
> nothing useful about :IR, I will remind them that IsProvable(P) is not
> the same as !IsProvable(!P).  Knowing that something has been "tagged"
> as an :IR may indeed be useful to some applications.)
>
> I think a way to state the chimera case
> http://www.w3.org/2001/tag/awwsw/issue57/latest/#id35999
> is to say that an HTTP GET of u returning a 200 status implies:
>
>  <u> a :IR ; log:uri "u" .       # Assertion set gh

With the :accessibleVia predicate there is no need to provide the type
assertion. *Any* unnecessary use of IR as a type (which I think is all
uses) has to be avoided, since otherwise the case for IRs is weakened
by an appearance of decree.

>
> Let's call this set of assertions "gh" (graph implied by the HTTP
> response).
>
> Then, if the document retrieved from u happens to be interpretable as
> RDF, that RDF might further say something like:
>
>  <u> a :Toucan .                 # Assertion set gd
>
> Let's call this set of assertions "gd" (graph expressed in the URI
> declaration, or "account").
>
> But is :IR owl:disjointWith :Toucan?  Not necessarily.

That is not the question on the table. The question is whether any
member of :Toucan makes a good metadata subject - can they have topics
and authors and so on. That is really up to whoever is trying to talk
about :Toucans.

I don't know if you noticed but my IR theory really is strong enough
to let you conclude quite a bit about deployed IRs - it lets you write
metadata. Different metadata in each case, to be sure. The metadata in
itself may be enough to get someone to decide to mint a new URI rather
than use the one for the IR. In fact we don't really have anything
else to offer. Knowing something is an IR completely useless, since
nothing follows from that, but metadata is useful, and it follows from
what you GET (in aggregate).

The chimera case is simply that IR(u) = WS(u). The consequences of
that can be worked out in many different ways. I thought I covered
them pretty well with my three points. Maybe I missed something, or
wasn't clear - I can always use help being more complete and clear.

I have thought about trying to talk about interoperability in terms of
graph merging and consistency checking (= construction of satisfying
interpretations).  This is sort of weak since it's so hard to get an
inconsistency in RDF and most people won't have a clue what's being
discussed. It would be a lot easier with OWL but that would not make
us popular. I think it's better just to appeal to the reader's common
sense, especially since the main audience is people who [say they]
don't care about inference.

Examples will help. But I think introducing the "declaration" and
"owner" ideas or anything like them will very much weaken the report -
and I say this not just because I don't believe them, but because of
Occam's razor. People already have ideas of how all this works, and I
want to enlist and refine their existing understanding, not throw
something new at them. Remember the only purpose here is to start the
issue 57 conversation going.

Hey, here's an idea: rename "information resource" to "metadata
subject" throughout?

Jonathan

> But suppose
> someone else supplies another set of assertions "ga" (graph of ancillary
> statements):
>
>  :IR owl:disjointWith :Toucan .  # Assertion set ga
>
> Now an RDF consumer that chooses to merge graphs gh, gd and ga will
> obviously have a problem, because the result will be self-contradictory.
> It will either need to forgo some of these assertions, or it will need
> to split the identity of <u>.
> http://dbooth.org/2007/splitting/
>
> On the other hand a different RDF consumer may happily choose to merge
> only graphs gh and gd, thus allowing <u> to (ambiguously) denote
> something that is both an :IR and a :Toucan in the merged graph.
>
> Furthermore, a third RDF consumer may happily choose to merge only
> graphs gh and ga, thus viewing <u> as only an :IR.
>
> This brings us into the whole question of which assertions *should* be
> used in what circumstances, i.e., what should these graphs contain,
> which of them should be merged by whom under what circumstances, and
> what should be done if there are contradictions?
>
> There are several questions:
>
> 1. Precisely what assertions should be included in gh, the graph implied
> by the HTTP 200 response?  The n3 rules at
> http://www.w3.org/wiki/AwwswDboothsRules
> were intended as a first crack toward nailing this down.
>
> 2. What responsibilities does a URI owner have in minting a new URI,
> configuring his/her server, and hosting a URI declaration (or
> "account")?  Many people have talked about this, including the "Cool
> URIs for the semantic web" document:
> http://www.w3.org/TR/cooluris/
> and my papers on URI declarations:
> http://dbooth.org/2007/uri-decl/
> and "The URI Lifecycle in Semantic Web Architecture":
> http://dbooth.org/2009/lifecycle/
>
> 3. If a URI owner does host a URI declaration (or "account"), what
> assertions should it include or avoid?  For example, if gh asserts that
> <u> is an :IR, should the URI declaration (or "account") include a
> disjointness assertion like "<u> owl:disjointWith :Toucan" if <u> is
> *only* intended to denote a toucan?  This has mostly been only vaguely
> addressed in the past, however my paper on "The URI Lifecycle in
> Semantic Web Architecture"
> http://dbooth.org/2009/lifecycle/
> does propose that the URI declaration (or "account") should not contain
> any assertions that would cause the transitive closure of URI
> declarations (i.e., the ontological closure) to be contradictory.
>
> 4. What should be the RDF statement author's responsibilities, in
> writing a graph of statements involving <u>, to help ensure that the
> intended "meaning" of <u> will be understood by an RDF consumer?  The
> URI Lifecycle paper also proposed an answer to this question.
> http://dbooth.org/2009/lifecycle/
>
> 5. What process and graphs should the RDF consumer use, in attempting to
> determine the referent of a URI?  The URI Lifecycle paper proposes an
> (initial) answer to this
> http://dbooth.org/2009/lifecycle/
> and the paper on "Resource Identity and Semantic Extensions: Making
> Sense of Ambiguity"
> http://dbooth.org/2010/ambiguity/paper.html
> goes into much more detail on the proposed process or algorithm.
>
> All of these questions need more work before we can hope to reach
> community consensus, but we do at least have some starting points.
>
>
>
> --
> David Booth, Ph.D.
> http://dbooth.org/
>
> Opinions expressed herein are those of the author and do not necessarily
> reflect those of his employer.
>
>
Received on Friday, 18 March 2011 16:59:38 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Friday, 18 March 2011 16:59:39 GMT