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Re: Question regarding POST versus PUT for creating an LDPC

From: Arnaud Le Hors <lehors@us.ibm.com>
Date: Wed, 17 Apr 2013 08:11:10 -0700
To: public-ldp-wg@w3.org
Message-ID: <OFA277958F.9805E504-ON88257B50.00515C1B-88257B50.00536AC2@us.ibm.com>
Hi Cody,
The spec allows creating resources using PUT [1] but it recommends to POST 
to a container as a way to do so [2]. The spec further specifies that 
containers can be created the same way, since they are resources. [3]

[1] 4.4.6 LDPR servers MAY choose to allow the creation of new resources 
using HTTP PUT. 
[2] 5.4.1 LDPC clients SHOULD create member resources by submitting a 
representation as the entity body of the HTTP POST to a known LDPC. 
[3] 5.4.4 For servers that support create, LDPC servers MUST create an 
LDPR from a RDF representation in the request entity body. The LDPR could 
also be a LDPC, therefore servers may allow the creations of LDPCs within 
a LDPC. 

Now, you might ask: how do I start? That is currently left undefined. It 
is assumed that somehow you can get a hold of a first container.
Arnaud  Le Hors - Software Standards Architect - IBM Software Group

Cody Burleson <cody.burleson@base22.com> wrote on 04/17/2013 07:00:33 AM:

> From: Cody Burleson <cody.burleson@base22.com>
> To: "Eric Prud'hommeaux" <eric@w3.org>, 
> Cc: Linked Data Platform WG <public-ldp-wg@w3.org>
> Date: 04/17/2013 07:09 AM
> Subject: Re: Question regarding POST versus PUT for creating an LDPC
> First of all, thanks for your feedback.
> I understand the case of creating a resource within a container and 
> using the container as a factory for that. I think I understand the 
> case of creating a container.
> In the case that I am creating a named container, I am considering 
> the following:
> HTTP PUT (of type text/turtle) TO URI: http://base22.com/carbon/ourco
> @base <http://base22.com/carbon> .
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
> @prefix dcterms: <http://purl.org/dc/terms/>.
> @prefix ldp: <http://www.w3.org/ns/ldp#>.
> <>
>     a ldp:Container;
>     dcterms:description "A domain root container for OurCo resources.";
>     rdfs:comment "In a multitenant environment, Carbon LDP typically
> uses a root container after the servlet context to represent the 
> concept of the tenant (e.g. a site, application, or particular 
> domain of knowledge.";
>     rdfs:label "ourco".
> My thought is because I am PUTting to "/ourco" and an LDPC/LDPR does
> not yet exist at that URI, then the server can accept creation of 
> the container, which would henceforth be accessible at that URI.
> Does that sound about right?
> - Cody

> On Wed, Apr 17, 2013 at 5:38 AM, Eric Prud'hommeaux <eric@w3.org> wrote:
> * Cody Burleson <cody.burleson@base22.com> [2013-04-16 23:37-0500]
> > Team,
> >
> > I'm curious of your opinion.
> >
> > I have been feverishly trying to catch up, where time permits, by 
trying my
> > hand at implementing what is specified thus far (in Java, as a layer 
> > Tomcat).
> >
> > One area where I'm having doubts is on what might be the more logical 
> > method for the creation of an LDPC. POST or PUT?
> >
> > I kind of get the feeling that the spec, as it stands, seems to imply 
> > PUT is the better method. But I'm not so sure.
> >
> > In your experience, is there a convention for CREATE? It just doesn't 
> > clear to me that one is intended over the other. I suppose both could 
> > supported, but what would be the majority expectation?
> >
> > Or does it matter?
> >
> > Sorry - I know I'm not really contributing yet, but rather - just 
> > more questions. But I think, perhaps, that once I get my code up to a 
> > where it's starting to have good coverage, it may start to reveal some 
> > questions and issues that could add value. So, bear with me (and be 

> If the client knows or has control over the name of the resource to be
> created, it should PUT the contents to the new location. There are
> several problems with this caveat:
> 1 PUTting a resource names that aren't cryptographically unique means
>   it's likely that some client has already created that resource,
>   e.g. all clients try all the time to create container/item1.
> 2 The server implementation might constrain the names of the resources
>   it can store and serve, e.g. one backed by a database which stores
>   only an integer which it concatonates unto "container/item".
> For these reasons, LDP also supports the common web convention of
> POSTing to a factory to create new resources. In LDP's case, that
> factory is called a container and there is a prescribed protocol and
> media language for talking to it.
> Hope I answered the right question.
> > --
> > Cody Burleson
> --
> -ericP
> -- 
> Cody Burleson
> Enterprise Web Architect, Base22
> Mobile: +1 (214) 702-6338
> Skype: codyburleson
> Email: cody@base22.com
> Blog: codyburleson.com
> [image removed] 
> Check my free/busy time.
Received on Wednesday, 17 April 2013 15:24:13 UTC

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