Re: [apps-discuss] NEW RELATION: property and context

[Ioseb Dzmanashvili <[e-mail]>]

James, Markus, Thanks for taking discussion further! I'm at work right now and will write detailed responses later.

@Markus

> I would really like to understand the differences but so far I haven't seen any. Ioseb, maybe a couple of more concrete examples about how you see the two rels being used would help a lot. And maybe also mention why collection/item or describes/describedBy wouldn't work for those examples.

Here is the example:

*** REQUEST: Fetch photo ***
> GET /article/photo HTTP/1.1
> Host: service.org

*** RESPONSE: Photo representation ***
< HTTP/1.1 200 OK
< Content-Type: image/jpeg
< Content-Length: ...
< Link: </article/photo;prop1>; rel="property"; title="Property 1",
<   </article/photo;prop2>; rel="property"; title="Property 2",
<   </article/photo>; rel="self"; title="...",
<   </article>; rel="context" title="Thousand Leagues Under the Sea"
<    
< [BINARY DATA HERE]

*** REQUEST: Fetch one of the properties ***
> GET /article/photo;prop1
> Host: service.org

*** RESPONSE: property representation ***
< HTTP/1.1 200 OK
< Content-Type: text/plain
< Link: </article/photo;prop1>; rel="self" title="...",
<   </article/photo>; rel="context"; title="..."
<  
< [PROPERTY VALUE HERE]


Based on this example, i'm not sure how the "describes" link relation can be used instead of the "context" link relation when by definition the "describes" relations says that: "The relationship A 'describes' B asserts that resource A provides a description of resource B. There are no constraints on the format or representation of either A or B, neither are there any further constraints on either resource."? In this particular example "context" indicates resource to which the /article/photo or /article/photo;prop1 resources belong and  context resources do not provide any description of those members.  What i want to say here it's a simple relationship between two resources without any descriptions etc…

Same with the "collection" and "item" relationships, i do not see(or maybe do not understand?) how /article and /article/photo resources are collections? if yes, collections of what? generally we can say that everything is an item but taking the definition of the "item" link relation: "The target IRI points to a resource that is a member of the collection represented by the context IRI." Now if we consider following example:

< HTTP/1.1 200 OK
< Content-Type: …
< Content-Length: …
< Link: </article>; rel="self"; title="…",
<    </article/photo>; rel="enclosure" title="…"
<
< [REST OF CONTENT HERE]

can we say for /article/photo resource that context IRI represents a collection? or does the /article resource somehow "describes" the /article/photo resource? or is /article/photo resource is an item which belongs to collection?  

Hope these examples will help! will write more later today. Thanks again!

cheers,
isoeb


On Wednesday, May 29, 2013 at 4:38 AM, Markus Lanthaler wrote:

> On Wednesday, May 29, 2013 2:21 AM, James M Snell wrote:
> > > James, did you read all the discussion? Ioseb made it quite clear
> >  
> > that his
> > > "context" is intended to be used completely different than JSON-LD's
> > > context. I'm still not sure I understand its semantics.
> > >  
> >  
> >  
> > Yep, I saw that and purposefully chose to ignore it :-) ... given the
> > general definition of "context" given in the draft, use for json-ld
> > type scenarios is not ruled out.
> >  
>  
>  
> Well.. the problem I have with the current I-D is that even after all these discussions I still don't understand what "context" is supposed to mean. Quoting the I-D:
>  
>  
> When included in a response, the "context" link relation identifies a
> target resource that represents a context document of which the
> context resource is a member.
>  
> For example, if a resource represents the property of a photo, that
> same resource may include link to a resource which the property
> belongs.
>  
> Taking the second paragraph, wouldn't the "describes" relation achieve just that? Quoting the abstract of RFC6892 which defines "describes":
>  
> This specification defines the 'describes' link relation type that
> allows resource representations to indicate that they are describing
> another resource. In contexts where applications want to associate
> described resources and description resources, and want to build
> services based on these associations, the 'describes' link relation
> type provides the opposite direction of the 'describedby' link
> relation type, which already is a registered link relation type.
>  
>  
> I would really like to understand the differences but so far I haven't seen any. Ioseb, maybe a couple of more concrete examples about how you see the two rels being used would help a lot. And maybe also mention why collection/item or describes/describedBy wouldn't work for those examples.
>  
>  
> Cheers,
> Markus
>  
>  
> --
> Markus Lanthaler
> @markuslanthaler
>  
>