Re: LDP-NR and Associated LDR-RS

On 10 Oct 2014, at 04:59, James Leigh <james@3roundstones.com> wrote:

> Hi,
> 
> It is not clear in the spec[1] if the associated LDP-RS should be
> included in the ldp:contains of the container along with the newly
> created LDP-NR. Something like the following phrases would work for me:
> 
> If a LDP server creates this associated LDP-RS, it MUST include both as
> members, and indicate the LDP-RS location in the repsonse...


So you mean that the LDPC should contain after the
POSTing of a cat picture should contain something like  
the following:

 <> ldp:contains <cat.jpg>, <cat.data>

My feeling is that all metadata created in addition to the 
created resource should disappear when the original resource 
dissapears, so that removing <cat.jpg> should also remove
<cat.data>. Otherwise deleting a resource is going to be really
tricky for a client: it would need to know what the acl for the resource
was, what the metadata for an LDP-NR was, etc and DELETE each of those.
The number of these resources could grow as the protocol evolves, so
that old clients would always be broken on new servers.

so my reading of the ldp:contains relation is that it lists
the resource created directly on a POST or PUT. All other
resources are server managed and presumably dissapear with
it too. 

It would seem more in line with the current spec that the LDPC
contains something like the following

 <> ldp:contains <cat.jpg> .
                 <cat.jpg> ldp:describedBy <cat.data> .

of course you could have

  <> ldp:contains <cat.jpg> .
                  <cat.jpg> a mime:image;
                            html:width "400"^^html:pixels ;
                            html:height "350"^^html:pixels .

In which case 

  <cat.jpg> ldp:describedBy <> .

But notice that this helps explain why the metadata generated
on creation of a resource should dissapear. a metadata resource
such as <cat.data> is just a way of placing the data that could
be in the LDPC outside of it. And clearly the data in the ldpc
that is about a contained resource disspears on the deletion 
of that resource.

On the other hand all of the above should perhaps be made clearer.

Henry


> 
> Thanks,
> James
> 
> [1] http://www.w3.org/TR/ldp/#ldpc-post-createbinlinkmetahdr
> 5.2.3.12 Upon successful creation of an LDP-NR (HTTP status code of
> 201-Created and URI indicated by Location response header), LDP servers
> MAY create an associated LDP-RS to contain data about the newly created
> LDP-NR. If a LDP server creates this associated LDP-RS, it MUST indicate
> its location in the response by adding a HTTP Link header with a context
> URI identifying the newly created LDP-NR (instead of the effective
> request URI), a link relation value of describedby, and a target URI
> identifying the associated LDP-RS resource [RFC5988].

Social Web Architect
http://bblfish.net/

Received on Friday, 10 October 2014 08:52:00 UTC