Re: representing hypermedia controls in RDF

Mike,

so if RDF representation includes a triple such as

  <http://example.com/xxxxx> a foaf:Image .

is that an affordance? Because that gives me enough information to
render it as <img src="http://example.com/xxxxx"/>.

By the way, nothing stops me from having <a href="isbn:343-224122">
either. It will probably be clickable, but won't work.

Martynas

On Fri, Nov 22, 2013 at 4:42 PM, mike amundsen <mamund@yahoo.com> wrote:
> <snip>
> A browser for example doesn't render the string
> http://example.com/343-224122 as a clickable link unless you mark it up as
> one using the <a> tag.
> </snip>
>
> Yep, the A element is the thing that _affords_ clicking. it is the A element
> which is the affordance.
>
> Affordances don't just supply addresses, they supply information about what
> you can _do_ with that address (navigate, transclude, send arguments, write
> data, remove data, etc.). The appearance of a URL alone provides very little
> affordance.
>
> For example:
> - http://example.com/xxxxx
> - http://example.com/yyyyy
> one of the two URLs points to a blog page to which the user can navigate,
> the other points to a logo which should be displayed inline. which is which?
>
> Now this:
> - <a href="...">blog</a>
> - <img href="..."  />
> one of the two URLs points to a blog page, the other points to a logo. which
> is which?
>
> Note it is not the URL that provides the information (which is for
> navigation, which is for transclusion), but the element in which the URL
> appears. The element is the affordance. These are HTML affordances. There
> are a couple more hypermedia affordances in HTML. Other message models
> (media types) contain their own affordances.
>
> It is the appearance of affordances within the response representation that
> is a key characteristic of hypermedia messages.
>
>
>
> mamund
> +1.859.757.1449
> skype: mca.amundsen
> http://amundsen.com/blog/
> http://twitter.com/mamund
> https://github.com/mamund
> http://www.linkedin.com/in/mamund
>
>
> On Fri, Nov 22, 2013 at 10:13 AM, Markus Lanthaler
> <markus.lanthaler@gmx.net> wrote:
>>
>> Hi Martynas,
>>
>> On Friday, November 22, 2013 3:12 PM, Martynas Jusevičius wrote:
>> > Markus,
>> >
>> > in the Linked Data context, what is the difference between
>> > "identifier" and "hyperlink"? Last time I checked, URIs were opaque
>> > and there was no such distinction.
>>
>> These things quickly turn into philosophical discussions but simply
>> speaking
>> the difference lies in the expectations of a client. In XML for example,
>> namespaces are just identifiers. There's no expectation that you can go
>> and
>> dereference that namespace identifier (even though in most cases they use
>> HTTP URIs). The same is true about RDF. All URIs are just identifiers.
>> From
>> an RDF point of view, there's no difference between isbn:343-224122 and
>> http://example.com/343-224122. As you say, they are opaque.
>>
>> But if you build applications, it is important to distinguish between
>> identifiers and hyperlinks. A browser for example doesn't render the
>> string
>> http://example.com/343-224122 as a clickable link unless you mark it up as
>> one using the <a> tag.
>>
>> Linked Data advocates that all URIs are dereferenceable. But that's
>> communicated out of band. Apart from JSON-LD, which states that URIs
>> SHOULD
>> be dereferenceable, no other RDF media type makes such a statement. Thus
>> you
>> need to use constructs such as hydra:Link and hydra:Resource to make the
>> distinction explicit.
>>
>> Hope this helps. If not, let me know.
>>
>>
>> --
>> Markus Lanthaler
>> @markuslanthaler
>>
>>
>

Received on Friday, 22 November 2013 17:17:23 UTC