Re: Affordances wiki page

Kingsley,

agreed, linked data is about using dereferenceable URIs everywehere, so
that everyone can discover the meaning of a URI they do not know.

This is only one kind of affordance, though, and a client *has* to start
with some built-in knowledge for a set of URIs (just like someone can not
learn a new language by relying on a dictionnary, as every word is
described by other words).

My argument was that other kinds of affordance as possible as well,
provided that you know how to interpret a given (set of) triple(s) -- not
only by dereferencing every URI "blindly".

  pa


On Mon, Mar 4, 2013 at 12:16 PM, Kingsley Idehen <kidehen@openlinksw.com>wrote:

>  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> wrote:
>
>> hello john.
>>
>> On 2013-03-03 18:41 , "John Arwe" <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/RdfAffordancespage
>> 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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