Re: A parable about RFC 3986.

On Fri, 2012-01-27 at 15:27 -0500, Jonathan A Rees wrote:
> On Thu, Jan 26, 2012 at 11:19 AM, David Booth <david@dbooth.org> wrote:
> > I would paraphrase these architectures as:
> >
> >>   A. The Ian Davis architecture - a GET/200 URI can identify anything.
> >
> >  "By fiat, a GET/200 response means that the URI identifies that
> >  web resource, UNLESS the response content is an RDF/XML document,
> >  in which case the URI identifies whatever the RDF/XML document
> >  says it identifies."
> 
> This is not what I meant - I was referring to the "take at face value"
> architecture which should more properly be attributed to Harry Halpin
> and Manu Sporny - Ian's is similar and I wasn't referring to the
> conneg details. So replace 'Ian Davis' with 'Harry Haplin' in what I
> wrote before.

Okay.

> 
> >>   B. The Roy Fielding architecture - a GET/200 URI identifies a "fiat"
> >> (REST) resource.
> >
> >  "By fiat, a GET/200 response means that the URI identifies that
> >  web resource."
> 
> I don't know what a 'web resource' is 

I explained it later in my message:

   (I'm using the term 'web resource' instead of 'information resource'
   to avoid the assumption that they are disjoint with anything.)

> and Fielding doesn't use that term.  He doesn't in fact use any term
> other than 'resource'. 

Right, because in the Fielding architecture there is no need to
distinguish "information resource" from "resource".  But to compare the
three architectures, I used the same term when, it seems to me, they're
pretty much talking about the same things.

> I
> sometimes use 'REST resource' although it's not obvious to me that RFC
> 2616 and 3986 are talking about the same abstraction as the subject of
> the REST writing.
> 
> When I say 'Fielding architecture' here I mean what 2616 and 3986, and
> especially HTTPbis, describe (to the extent they describe anything).
> My conjecture is that my idea of 'fiat resource' coincides with what
> 2616 and 3986 would imply for resources permitting retrieval that are
> identified by http: URIs. But the details are subtle.
> 
> >>   C. The TimBL architecture - a GET/200 URI identifies a "generic"
> resource.
> >
> >  "By fiat, a GET/200 response means that the URI identifies that
> >  web resource.  And don't mint a URI that ambiguously identifies
> >  both a web resource and a toucan, because toucans are not web
> >  resources!"
> 
> I don't know where you get this; TimBL's view is entirely about what
> properties these things have, not what their type is; it's about
> titles and authors and subjects and licenses. 

I got it from AWWSW section 2.2, which defines "information resource":
http://www.w3.org/TR/webarch/#p43
"Other things, such as cars and dogs (and, if you've printed this
document on physical sheets of paper, the artifact that you are holding
in your hand), are resources too. They are not information resources,
however, because their essence is not information."

If that isn't what you mean by TimBL's view, then I don't know what you
mean by "TimBL's view".

> If someone wants to say
> that a toucan has a title, author, etc. that's not reasonable but it's
> their prerogative (in my view). 

I realize that may not seem reasonable if you assume that a URI
*uniquely* identifies a resource.  But if you believe that a URI is not
-- and in general can never be -- completely unambiguous about the
resource that it identifies, then it is perfectly reasonable so say such
things, for example, when that URI ambiguously identifies both the
toucan and a document.

> Maybe the right moniker is the JAR
> architecture, but I think Tim and I are mostly on the same wavelength
> so I prefer to attribute it to him.
> 
> And we've had the ambiguity/identity discussion before on the list
> without resolution, so I don't know why you bring it up, without
> bringing new information to the table.

Because it is still relevant, still central to understanding why this
has been such a devil of a knot to untie, and still difficult to convey.

> 
> I said that 'generic resources' are also 'fiat resources' but now I'm
> not so sure - if TimBL thinks Moby Dick is a generic resource, and
> he's right, then not all generic resources are fiat, since Moby Dick
> is not fiat. There may be a tighter class 'fiat generic resource' that
> is of interest, making yet another architecture.
> 
> Enumerating these classes has nothing to do with disjointness, it is
> about keeping track of what axioms you want to consider. There may be
> consistent models in which there exist things not in any given class
> (fiat resource etc.), but there may also be consistent models in which
> there are not.

Okay.  If you could be explicit about what those axioms are, it would be
very helpful in understanding what you mean.

> 
> I believe I have a moderately rigorous treatment that works and will
> send it under separate cover after I can get it independently checked.
> The quarter-baked 'parable' email was just to get some feedback, and I
> suppose I deserved what I got.

Sounds good.  I look forward to reading it.


-- 
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, 27 January 2012 21:30:03 UTC