>Since we are having such a good time with this...
>First, thanks, Pat. I am happy that someone who is connected to the
>process has added some clarification as to the current state of
>standards activities in this area. The debate is ongoing, and this
>forum is not in a position to influence it much. But we do need to
>know what direction that debate is taking, whether for better or
>worse, because it will influence the way in which we are able to
>speak, whether it be the way we prefer to think or no.
>>>Whoa! I fully agree that URLs locate lots of useful and functionally
>>>different things, just as postal addresses do. But if today it's a bank and
>>>tomorrow it's a laundry or a residence or a casino, what
>>>"resource" is being "identified"?
>>Well, according to Roy Fielding's REST model, which is endorsed by
>>the TAG, a resource is a function from times to 'representations'
>>(which I think here means not descriptions, but more like the sense
>>in which the webpage that my browser shows me is a 'representation'
>>of the state of your website at the moment I pinged it). So, the
>>answer is: the (note, singular) resource is a temporal function
>>whose value is in quick succession a representation of a bank, then
>>of a laundry, then a casino, etc...
>Well, I have to admit that that is a model I had never before heard
>promulgated. So I am at least grateful for the education. You will
>pardon my reaction that this is, to borrow a Russian metaphor, an
>attempt to make candy from manure. (01)
Ahem. I am only the messenger here, you understand. But to cut these
guys some slack, I see where they are going. If we reel back to the
very beginning of the Web, its clear people were thinking of a
world-wide network of hyperlinked documents. But as the Web grew up,
all kinds of things are now on websites which aren't anything like
documents. Webcams, RSS feeds, updated weather forecasts, radar
images, etc.. What *general* story can one give that accommodates
such things? One can see how one would be led inexorably to a
theoretical model in which the 'thing' that a URI identifies has to
be allowed to be something that returns a different 'representation'
of itself at each moment. Perhaps they should have said, of its state
at that moment: but even that presumes that there is a stable entity
which has a 'state', and I gather that there are real-life examples
of 'resources' that this would be a misleading account of. (02)
I think what has happened is that the actual practice of the Web has
always been slightly ahead of any theoretical model; and Roy made a
very brave attempt to come up with an overarching account which would
not be immediately rendered obsolete. The cost, of course, it that is
so general that at times it almost seems vacuous, and its easy to
reduce it to absurdity by following its rules without being
'sensible'. But in fact, this is more the fault of its surrounding
prose than of the REST model itself. So for example this awful word
"resource" has been adopted, I think, because almost any other word
is too limiting (document, text, file, ... none of them covers a
webcam, or a 3-d milling machine hooked up to a Web-based server for
parts prototyping, or a home security system, or a website which is
running on a UAV flying over Baghdad, or...) (03)
>>This seems to make nonsense of the TAG assertion that URIs "ought"
>>to be stable, indeed eternal, in the sense that they should always
>>identify the same resource; since there seems to be no way to
>>distinguish a single resource which looks like a chameleon from a
>>succession of resources each of which is rather more stable. I
>>asked the TAG to clarify this point, but they didn't take up the
>The "clarification" would doubtless have been a misnomer in any case.
>>>What I said was that if the content to which a URI refers changes radically
>>>from day to day, the URI doesn't identify "an information
>>>resource" in any useful sense.
>>But it can still technically identify a single resource. There
>>really are sites like this, eg http://www.humanclock.com/clock.php
>>which changes every minute.
>This goes to my observation (below) that the "nature" of a resource
>is some combination of content, function and behavior. The clock
>has constant function and behavior. The exact content changes to
>fulfill that function, but the "functional content" is always the
>same -- it is the current population of the world. (04)
Actually that clock is just the time, told in an amusing way. But
your point is still valid. There is a meaningful 'account' of what
the resource "is", which is what makes it a 'genuine' or 'sensible'
resource. But imagine, say, a video artist who sets up a website
which is deliberately randomized in its response. It has no rationale
at all, which is (let us suppose) the artist's point. Is this a
resource? Well, I think the TAG's position (and Roy's) would be,
sure, why not? Certainly from the purely *architectural* point of
view - which is what the TAG is supposed to be considering - there is
no real difference between a mere document plonked at a location and
this crazy thing. They are both GET-endpoints which when
appropriately pinged, deliver a bitstream; and that is all they have
to be. (05)
>But it is exactly this kind of variance that tells us we can't in
>general equate the "resource" at the location with the text of the
>web page. The question here is whether the "information content of
>the web page" is the "population of the world at 17:00 UTC on 16
>April 2007", or the "current population of the world", which are
>clearly distinguishable concepts. I would not be uncomfortable
>arguing that the humanclock location corresponds to a "resource"
>that is a "service" rather than a "document". (06)
Right, and I think Roy might be happy with this also. Certainly,
"resource" is intended to be wider in scope than "document". Seems to
me that what the TAG really mean by "resource", though they won't let
themselves say so, is an http: endpoint. Or rather, since there can
of course be non-http protocols, an endpoint for some Web-defined
transfer protocol. That definition would at least make sense.
Unfortunately (IMO) , the TAG have decided that the 'protocol' sense
of "identify a resource" must coincide with the referent of a URI
when it is used as a logical name; and since one can *refer* to
anything, then a resource can be *anything*. We have still not got
out of the resulting muddle. (See
http://www.ibiblio.org/hhalpin/irw2006/presentations/HayesSlides.pdf ) (07)
>>> And thus the idea that the URI identifies something different
>>>from a location is false. If the purpose of a URI is to denote content,
>>>function, behavior, as distinct from location, some one of those
>>>has to be consistent over time.
>If the content, function, and behavior of whatever is at the
>location have no commonalities over time, then all that is being
>designated is the location. It's a particular street corner, full
>stop. It is not THE location OF anything in particular, except
Well, two responses. First, who is to say what counts as a
commonality? (Consider the artist example above). And second, why
does it matter? That is, why do we need to require that resources
meet some criterion of 'sensibleness? Even if it is only a location,
its the location of whatever happens to be at that location. Which is
circular, I grant you, but not incoherent. And there are quite
sensible examples which fit into this very dynamic model but won't
fit into anything more static. (09)
>>> A bulletin board and a pulpit are just locations.
>>>>Everything is a resource to someone, as it should be. What we want to
>>>>be able to do is differentiate resources so we use the one(s) most
>>>>suitable for our needs.
>>>Exactly. But unless there are common conventions for that
>>>differentiation, all we have is a bunch of disorganized resources
>>>labeled according to hundreds
>>>or thousands of incompatible schemes, most of which are not very
>>>good or very
>>>useful. Google has built a successful enterprise on the failure of the Web,
>>>and its principal resources, to address that problem. And there
>>>are many who
>>>believe that that also is as it should be.
>>Close. I believe that this is the way it WILL be, no matter how
>>much any number of people try to improve it. So we ought to get
>>used to reality, and learn how to deal with it :-)
>I find myself having to agree.
>I often cite the Serenity Prayer (attributed to Reinhold Niebuhr):
>Grant me the serenity to accept the things I cannot change,
>The courage to change the things I can,
>And the wisdom to know the difference.
>This does not, however, prevent me from undertaking efforts which I
>believe to have a very low probability of success, if only to
>fulfill Alexei Meystel's observation that "someday, someone will
>remember that this was said, and it will make a difference."
>In engineering, you can't prevent the design, manufacture and sale
>of junk. But you can teach young engineers how to design and build
>quality, in the expectation that a few of them will actually have
>the opportunity. (010)
I think this is the way the TAG group sees its role. Certainly how
TimBL does. Theres a strange zone somewhere between description and
exhortation. A bit like descriptive vs. proscriptive linguistics,
come to think of it. (011)
>>>IMO, the problem is that Internet is still the big city of the
>>>Middle Ages. ...
>>Following your analogy, the other thing about the internet is that
>>it is getting bigger faster than we are learning how to use it.
>>living on an expanding planet.
>Absolutely. But I think we are also only beginning to see the
>seismic instability that goes with planetary expansion, the
>consequent threat to fragile economic and social structures, and the
>draconian countermeasures the establishment will impose to protect
>itself from seismic events. That too is how it WILL be, and that
>future may well be less rosy than the present.
>>Maybe thats why it stays rather like the wild west.
>My favorite analogy for the Internet has always been the Wild West.
>(I can't say what possessed me to choose the late medieval city on
>this go.) ;-) (012)
Yeee-Haww :-) (013)
>Edward J. Barkmeyer Email: edbark@xxxxxxxx
>National Institute of Standards & Technology
>Manufacturing Systems Integration Division
>100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
>Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694
>"The opinions expressed above do not reflect consensus of NIST,
> and have not been reviewed by any Government authority." (015)
BTW, does putting this in quotes make it less of an assertion? (016)
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