Re: Affordances wiki page

On 3/4/13 6:33 AM, Pierre-Antoine Champin wrote:
> Erik,
>
> I agree with you that RDF in itself does not provide affordances, and 
> that the fact that it uses URIs does not mean that those URIs are 
> links (in the hypermedia/REST sense).

Yes, that's true re. RDF.

RDF based Linked Data on the other hand do require HTTP URIs to provide 
specific behavior i.e., said URIs resolve to documents that describe the 
URI's referent. Every RDF based Linked Data document bears content that 
describes something. The content takes the from of an RDF model based 
entity relationship graph.

>
> I think, however, that (RDF + some built-in knowledge about a given 
> vocabulary) does provide affordances.

As per comment above, when talking about RDF based Linked Data since the 
"Linked Data" part is where the affordances come into play re. link 
behavior.

> For example, a client knowing what foaf:depication means can use it to 
> provide a better representation of the depicted resource.

Only if the entity in question is denoted using a de-referencable URI 
(e.g., an HTTP URI).
>
> The goal of the LDP recommendation is to describe the built-in 
> knowledge that all LDP-client are expected to have about the ldp: 
> vocabulary. And this knowledge about the ldp: vocabulary should apply 
> to *any* RDF graph that the client encounters, regardless of the 
> media-type it got it from (Turtle, RDF/XML, RDFa...). So I disagree 
> with you that we need a specific media-type for LDP.

Correct, this argument with Erik is basically been going on forever. It 
resolution can only truly occur via solution implementation and 
demonstration.

RDF != Linked Data.

RDF based Linked Data is what LDP is based on. Thus, the affordances and 
everything else are totally baked in, as Henry has demonstrated 
repeatedly via the use of ontology definition to navigate these matters.

>
> Of course, it would be good to provide the client with a hint of the 
> vocabularies it can expect to find in some RDF, even *before* parsing 
> it. This is where I think your profile proposal adds some value, as 
> something *orthogonal* to the media-type.

In reality, the whole thing (RDF based Linked Data) is a close loop. The 
challenge is getting to the point where ontologies/vocabularies and 
demonstrations drive the LDP dialog instead of prose.

RDF based Linked data is a fusion of data representation, access, and 
first-order logic. It's all about relations and their semantics.

Kingsley
>
>   pa
>
>
> On Mon, Mar 4, 2013 at 9:50 AM, Wilde, Erik <Erik.Wilde@emc.com 
> <mailto:Erik.Wilde@emc.com>> wrote:
>
>     hello john.
>
>     On 2013-03-03 18:41 , "John Arwe" <johnarwe@us.ibm.com
>     <mailto:johnarwe@us.ibm.com>> wrote:
>     >Erik, your HTML example strengthens the suspicion that had been
>     growing
>     >in me about your initial response (paraphrased playback) "the rows on
>     >that page are not affordances", i.e. about how you were using the
>     word.
>     >As you're
>     > using it, affordances are at a higher level of abstraction and
>     what the
>     >wiki page lists (or did, last I looked - on a plane now so unable to
>     >check) are "just" spec options - things overtly relegated to
>     >implementation choice.  Those would have an n:m relation
>     > with affordances, by your definition.  Getting closer?
>
>     do you have any idea where the
>     http://www.w3.org/wiki/RdfAffordances page
>     originates? i would argue that it contains some really misguided
>     ideas,
>     such as looking at the URIs in RDF as links. this mixes RDF's data
>     model
>     (which happens to be URI-based) with an entirely different issue,
>     which is
>     the question of how to represent hypermedia affordances (now i am
>     using
>     the term as i am used to it from the hypermedia/REST community),
>     and once
>     you start doing that, i don't think there's any way to get out of this
>     initial conflation of concepts.
>
>     for me, affordances are the critical parts of hypermedia formats that
>     guide clients through the media type, allowing them choices of
>     navigational paths while they are traversing the interlinked set of
>     resources exposed as hypermedia. RDF doesn't have anything to
>     contribute
>     here as it doesn't have links. so affordances (again, in my view
>     of the
>     term) would be the kinds of things a hypermedia format such as LDP
>     would
>     add, saying "when you find this link in a representation, then you can
>     follow it, and you have to interact in the following way when you
>     follow
>     it, and then you can expect the following thing to happen."
>
>     cheers,
>
>     dret.
>
>
>


-- 

Regards,

Kingsley Idehen	
Founder & CEO
OpenLink Software
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