On 12 June 2011 01:51, Pat Hayes <[email protected]> wrote: > > On Jun 11, 2011, at 12:20 PM, Richard Cyganiak wrote: > >> ... >>>> It's just that the schema.org designers don't seem to care much about the >>>> distinction between information resources and angels and pinheads. This is >>>> the prevalent attitude outside of this mailing list and we should come to >>>> terms with this. >>> >>> I think we should foster a greater level of respect for representation >>> choices here. Your dismissal of the distinction between information >>> resources and what they are about insults the efforts of many >>> researchers and practitioners and their efforts in domains where such >>> a distinction in quite important. Let's try not to alienate part of >>> this community in order to interoperate with another. >> >> Look, Alan. I've wasted eight years arguing about that shit and defending >> httpRange-14, and I'm sick and tired of it. Google, Yahoo, Bing, Facebook, >> Freebase and the New York Times are violating httpRange-14. I consider that >> battle lost. I recanted. I've come to embrace agnosticism and I am not >> planning to waste any more time discussing these issues. > > > Well, I am sympathetic to not defending HTTP-range-14 and nobody ever, ever > again even mentioning "information resource", but I don't think we can just > make this go away by ignoring it. What do we say when a URI is used both to > retrieve, um sorry, identify, a Web page but is also used to refer to > something which is quite definitely not a web page? What do we say when the > range of a property is supposed to be, say, people, but its considered OK to > insert a string to stand in place of the person? In the first case we can > just say that identifying and reference are distinct, and that one expects > the web page to provide information about the referent, which is a nice > comfortable doctrine but has some holes in it. (Chiefly, how then do we > actually refer to a web page?) But the second is more serious, seems to me, > as it violates the basic semantic model underlying all of RDF through OWL and > beyond. Maybe we need to re-think this model, but if so then we really ought > to be doing that re-thinking in the RDF WG right now, surely? Just declaring > an impatient agnosticism and refusing to discuss these issues does not get > things actually fixed here.
For pragmatic reasons I'm inclined towards Richard's pov, but it would be nice for the model to make sense. Pat, how does this sound: >From HTTP we get the notions of resources and representations. The resource is the conceptual entity, the representations are concrete expressions of the resource. So take a photo of my dog - <http://example.org/sasha-photo> foaf:depicts <http://example.org/Sasha> . If we deref http://example.org/sasha-photo then we would expect to get a bunch of bits that can be displayed as an image. But that bunch of bits may be returned with HTTP header - Content-Type: image/jpeg or Content-Type: image/gif Which, for convenience, lets say correspond to files on the server called sasha-photo.jpg and sasha-photo.gif Aside from containing a different bunch of bits because of the encoding, sasha-photo.jpg could be a lossy-compressed version of sasha-photo.gif, containing less pixel information yet sharing many characteristics. All ok so far..? If so, from this we can determine that a representation of a resource need not be "complete" in terms of the information it contains to fulfill the RDF statement and the HTTP contract. Now turning to http://example.org/Sasha, what happens if we deref that? Sasha isn't an information resource, so following HTTP-range-14 we would expect a redirect to (say) a text/html description of Sasha. But what if we just got a 200 OK and some bits Content-Type: text/html ? We are told by this that we have a representation of my dog, but from the above, is there any reason to assume it's a complete representation? The information would presumably be a description, but is it such a leap to say that because this shares many characteristics with my dog (there will be some isomorphism between a thing and a description of a thing, right?) that this is a legitimate, however partial, representation? In other words, what we are seeing of my dog with - Content-Type: text/html. is just a very lossy version of her representation as - Content-Type: physical-matter/dog Does that make (enough) sense? Cheers, Danny. -- http://danny.ayers.name
