Re: superimposing the Fielding and TBL architectures

On Tue, Sep 27, 2011 at 6:36 PM, David Booth <david@dbooth.org> wrote:
> Pat's comments about resource state reminded me that I meant to make
> another comment about the diagram:
>
> Regarding the "records the current state of" relation, are you
> intentionally omitting the effects of the request inputs?  In general,
> the result of an HTTP GET request (for example) depends both on the
> resource state *and* on information in the request.  Most obviously this
> would include things like language and media type preferences, but the
> specs are clear that the response can actually depend on anything in the
> request.

w:Representations are correct for a URI only under certain
circumstances,  i.e. assumptions about independent variables such as
request parameters, time, weather in Oaxaca. One could elaborate the
theory by talking about sets of "contingent wa:Representations" each
consisting of a wa:Representation together with a class of
circumstances. I've talked about this elsewhere and it's a distraction
so I didn't want to get to it.

> I suggest omitting the "records the current state of" relation.  You
> already have the "has 3986-representation" relation going the other way.

Since the two are the same there is no harm in putting both. This diagram was
just for talking about anyhow; I don't plan to work on it further.

> David
>
>
>
> On Tue, 2011-09-27 at 12:56 -0400, David Booth wrote:
>> On Tue, 2011-09-27 at 12:01 -0400, Jonathan Rees wrote:
>> > Mulling over designs for httpRange-14(a) opt-in, I made a picture
>> > (attached), just for fun, that superimposes the Fielding/3986
>> > architecture with the TimBL architecture.
>> >
>> > What stands out is the common ground: There is general agreement on
>> > what constitutes a correct retrieval operation using a URI. The
>> > agreement derives from the RFCs and from server and client behavior.
>> > This is invariant as we modulate theories of what the resource is and
>> > what "is a representation of" means.
>> >
>> > In the Fielding architecture the resource is unconstrained. I can give
>> > you a bunch of different resources, and then when you challenge me to
>> > prove that there is a resource with those Fielding-representations, I
>> > can cook up any story I like, post hoc, and you'd have no way to prove
>> > me wrong.
>> >
>> > In Tim's architecture the resource is determined, modulo usually we
>> > probably don't care about, by what the correct retrieval results would
>> > be. Once those results are determined, there's no choice as to what
>> > the resource is. Contrariwise, if the server side commits to what the
>> > resource is, we can hold them to it by checking any
>> > TBL-representations that they deliver.
>>
>> I don't know what you mean by saying "the resource is determined".  It
>> seems to me that the key difference (in this regard) between Tim's view
>> and Roy's is that Tim's view attempts to distinguish "information
>> resources" from other resources, and the "has TBL-representation"
>> relation only holds with information resources, whereas Roy's view has
>> no need for such a distinction: *any* resource can have a
>> wa:Representation.
>>
>>
>> >
>> > httpRange-14(a) opt-in would be a statement or protocol element that
>> > says that the URI Fielding-identifies the generic resource (i.e. the
>> > same thing that it TBL-identifies).
>>
>> But then what would be the difference between a wa:GenericResource and
>> an rfc3986-resource?  For example:
>>
>>   :u a xsd:anyURI .
>>   :x a wa:GenericResource .
>>   :x :is-TBL-identified-by :u .
>>   :y a :rfc3986-resource .
>>   :y :is-rfc3986-identified-by :u .
>>
>> What is the relationship between :x and :y ?  Are they the same thing?
>>
>> And does there exist a :rfc3986-resource :z such that :z has a
>> 3986-representation but :z is *not* a wa:GenericResource?  Or does the
>> mere existence of a 3986-representation imply that :z is a
>> wa:GenericResource?   (I.e., can there be a non-IR that has a
>> wa:Representation?)
>>
>> My own view is that the existence of an authorized wa:Representation
>> implies that the resource is a wa:GenericResource (or IR).
>>
>> David
>>
>> > Nothing much new here, pretty much what Pat has said in different
>> > words (although I put less stock in "access" and more in social
>> > agreement over what would constitute correct access were it to occur).
>> > Just noodling.
>> >
>> > Jonathan
>>
>
> --
> 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 Wednesday, 28 September 2011 12:41:49 UTC