Re: Example for consideration: Resource versus Representation

On Jan 23, 2008, at 12:51 PM, Pat Hayes wrote:

> At 11:34 PM -0500 1/22/08, Alan Ruttenberg wrote:
>> Are representations resources?
>
> They can be (anything CAN be a resource....), but its not usually  
> very useful to want to treat them as resources, I'd say.
>
>> I have heard the argument that they are not. In this morning's call  
>> I agreed to send an example I've been thinking about.
>> Consider some Information Resource that responds to a request with  
>> a Representation of type application/pdf.
>
> Wrong way to put it. You are making 'representation' into a  
> category, but it should be a relationship. That thing you get back  
> is required by the REST architecture to be a representation OF the  
> IR. That is, whatever we call this thing you get back, it bears a  
> webarch:represents relationship to the IR. Saying that doesn't say  
> what kind of thingthe representation is, only that it represents. So  
> we can (using this confusing language we all speak) nominalize this  
> and say that it 'is a representation', but that shouldn't be taken  
> to mean that this means (or at any rate, that it means usefully)  
> that it is a category of Things called Representations.

I'm content with saying something isn't useful. What I find to be a  
problem is the "can't be" which is what I hear.

>> I save the response on my hard disk. Is the thing I have  
>> (henceforth known as the file)  on my hard disk an Information  
>> Resource?
>
> Yes.
>> If it is, when and how did it become one, having been only a  
>> Representation until recently?
>
> When you stored it (in fact when you *created* that file, based on  
> the byte stream you got back from the first resource; that byte  
> steam being the actual representation of the first IR, if one wants  
> to be pedantic.)

(and wants to use that crazy nominalization thing we do ;-)

> Being a file, stored stably in a computer, it can possibly (see  
> below) be given a URI. However, I see no way to give a URI to a byte  
> stream.

True, but is this different that giving a URI naming "love".  What's  
the problem naming a byte stream with a URI, if we can name a person,  
process, property with a URI?

>
>> If not, what happens when I move the file to a directory (actually,  
>> I don't move the file, I make changes to directory structures) that  
>> my Apache server can serve from. Can my server respond to requests  
>> for Representations?
>
> No, because it doesn't know that this file represents anything, so  
> such a request is meaningless. But it can still serve the file.

Not that I'm sure which sense of "represents" you are using here, but  
even without knowing what it means, let me say two things: My apache  
server doesn't "know" anything. And I know it represents, since I know  
that it once represents, and I don't know how something that once  
represented comes to no longer represent. Moreover I can write that  
down in a comment about the resource and someone who read it could  
understand what I meant.

>
>> If not, how should it avoid serving this file? If the server  
>> answers requests only about Resources and is willing to serve the  
>> file then the file must be a Resource. If it is, same question:  
>> When and how did it become a Resource, having only recently been a  
>> Representation?
>>
>> It was suggested that perhaps Resources were only Resources if they  
>> were identified by a URI.
>
> I think that idea has been floated and rejected by the TAG before.  
> Its a resource if it can possibly be given a URI, even if it doesn't  
> have one yet.
>
> Pat
>
>> However this statement generated some controversy, so at least this  
>> is a point we should resolve.
>>
>> -Alan
>
>
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