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Re: URI Fragments

From: Nathan <nathan@webr3.org>
Date: Fri, 12 Mar 2010 16:46:51 +0000
Message-ID: <4B9A6FFB.20407@webr3.org>
To: Richard Cyganiak <richard@cyganiak.de>
CC: Linked Data community <public-lod@w3.org>
Thanks for your reply Richard,

I'm going to go "balls-out" today and challenge a bit of this for the
sake of argument:

Richard Cyganiak wrote:
> Hi Nathan,
> 
> On 12 Mar 2010, at 14:00, Nathan wrote:
>> Last question(s) related to fragments.. if I have:
>>  http://example.org/something
>>  http://example.org/something#a
>>
>> Those are two unique URIs and thus two unique resources (?)
> 
> Yes.
> 
>> And the semantics of a fragment means that
>> http://example.org/something#a is a secondary resource, where
>> http://example.org/something is the primary resource (?)
>>
>> Then if I delete a Primary resource, the secondary resources must also
>> be deleted, true / false (?).
> 
> Here's my take on this.
> 
> The web is about representations of information resources. If you add
> RDF to the picture, then it's also about descriptions of arbitrary
> entities.
> 
> On the web, you can create and delete representations. You can create
> and delete descriptions. But you cannot create or delete resources.

I'd argue that a resource is anything that can be named (or assigned a
URI), regardless of whether it has a representation or not. Even without
a representation a resource could still be reserved (which allows
references to be made to a concept before any realization of that
concept exists - although I've yet to confirm if 204 could be used for
this..); in another use-case though a resource like /news/latest may be
nothing more than a conceptual map to another resource (served via a 3xx
code) - this is a resource with no representation, which can be both
created and deleted surely?

In another case; let's say planned to lease a /London_Office (resource)
which I then described with a representation and 303'd to; then I
decided not to lease the /London_Office so deleted the representation
/and/ the resource because /London_Office isn't something that can be
named because it no longer exists, was never realized, and moreover I
want it removed because it was a painful loss.

Thus, can you delete resources? or another way, can you delete a
conceptual map?

I can't really respond to anything below this until the aforementioned
has been addressed; other than one small point.

> For example, if you do an HTTP DELETE request to a URI, the
> representations at that URI are deleted. As a side effect, something in
> your system (file, database record, purchase order) might be deleted as
> well, because your system intrinsically connects the representation to
> that system-internal entity, but that side effect is part of the
> application's internals and not a concern for the web interface.
> 
> So, you can't really “delete” those primary and secondary resources. But
> if you delete all the representations of a primary resource, then this
> will delete the authoritative descriptions of the secondary resources,
> because those live inside the representations.

if I remove the section and the reference test.html#whatever from
test.html; have I not deleted that secondary resource? it can't be named
any more, or referenced, or.. and so on

> Best,
> Richard
> 

Thanks again,

Nathan

>> Here are some examples, which may seem like over kill but some are
>> interesting and generally I *feel* rules like this should be either
>> always true, or always false, never varying.
>>
>> examples:
>> if I remove a database table, then all it's rows also no longer exist.
>> if I remove London then the Tower of London also no longer exists.
>> if somebody removes me, then my arms also no longer exist.
>> if I remove test.html then test.html#whatever no longer exists.
>> if I remove test.rdf then test.rdf#this no longer exists
>> if I remove http://www.w3.org/People/Berners-Lee/card then
>> http://www.w3.org/People/Berners-Lee/card#i no longer exists.
>>
>> conversely:
>> if I remove a row, the table still exists
>> if I remove the Tower of London, London still exists
>> if you remove my arms, I still exists and I'll find another way to type.
>> if I remove test.html#whatever test.html still exists
>> if I remove test.rdf#this, test.rdf still exists
>> if I remove http://www.w3.org/People/Berners-Lee/card#i then
>> http://www.w3.org/People/Berners-Lee/card still exists.
>>
>> If the above is true (secondary resource must also be deleted on removal
>> of primary resource), then I should never use a fragment Identifier to
>> refer to a non-virtual object (i.e. "me" a Person) - because I can't be
>> deleted by simply removing a resource. (?)
>>
>> Regards!
>>
>> Nathan
>>
> 
> 
> 
Received on Friday, 12 March 2010 16:47:36 UTC

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