Re: URI Fragments

[Richard Cyganiak]

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.

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.

Best,
Richard



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