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RE: How to avoid that collections "break" relationships

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Tue, 25 Mar 2014 16:52:16 +0100
To: 'Martynas Jusevičius' <martynas@graphity.org>
Cc: <public-hydra@w3.org>, "'W3C Web Schemas Task Force'" <public-vocabs@w3.org>, <public-lod@w3.org>
Message-ID: <009801cf4842$353a5350$9faef9f0$@lanthaler@gmx.net>
On Tuesday, March 25, 2014 2:11 PM, Martynas Jusevičius wrote:
> Vuk,
> If URIs like </alice> identify documents, then your example
> treats documents as persons. In other words, you conflate
> information resources and real-world resources.

Martynas, while this might be true, it doesn't really matter in the context
of this discussion. That's exactly the reason why I included the quite
explicit plea in my first mail:

> please let's not talk about hash URLs etc. here, ok?

So, please. Let's try to focus on the problem at hand.


Thanks,
Markus


--
Markus Lanthaler
@markuslanthaler



On Mar 25, 2014 11:35 AM, "Vuk Milicic" <vuk.milicic@eurecom.fr> wrote:
Hi Markus,

How about this:

</markus/friends/> rdfs:subClassOf schema:Person .
</alice> a </markus/friends/> .
</markus> schema:knows </alice> .


Vuk Milicic
@faviki


On 24 Mar 2014, at 16:24, Markus Lanthaler <markus.lanthaler@gmx.net> wrote:

> Hi all,
>
> We have an interesting discussion in the Hydra W3C Community Group [1]
> regarding collections and would like to hear more opinions and ideas. I'm
> sure this is an issue a lot of Linked Data applications face in practice.
>
> Let's assume we want to build a Web API that exposes information about
> persons and their friends. Using schema.org, your data would look somewhat
> like this:
>
>  </markus> a schema:Person ;
>            schema:knows </alice> ;
>            ...
>            schema:knows </zorro> .
>
> All this information would be available in the document at /markus (please
> let's not talk about hash URLs etc. here, ok?). Depending on the number of
> friends, the document however may grow too large. Web APIs typically solve
> that by introducing an intermediary (paged) resource such as
> /markus/friends/. In Schema.org we have ItemList to do so:
>
>  </markus> a schema:Person ;
>            schema:knows </markus/friends/> .
>
>  </markus/friends/> a schema:ItemList ;
>            schema:itemListElement </alice> ;
>            ...
>            schema: itemListElement </zorro> .
>
> This works, but has two problems:
>  1) it breaks the /markus --[knows]--> /alice relationship
>  2) it says that /markus --[knows]--> /markus/friends
>
> While 1) can easily be fixed, 2) is much trickier--especially if we
consider
> cases that don't use schema.org with its "weak semantics" but a vocabulary
> that uses rdfs:range, such as FOAF. In that case, the statement
>
>  </markus> foaf:knows </markus/friends/> .
>
> and the fact that
>
>  foaf:knows rdfs:range foaf:Person .
>
> would yield to the "wrong" inference that /markus/friends is a
foaf:Person.
>
> How do you deal with such cases?
>
> How is schema.org intended to be used in cases like these? Is the above
use
> of ItemList sensible or is this something that should better be avoided?
>
>
> Thanks,
> Markus
>
>
> P.S.: I'm aware of how LDP handles this issue, but, while I generally like
> the approach it takes, I don't like that fact that it imposes a specific
> interaction model.
>
>
> [1] http://bit.ly/HydraCG
>
>
>
> --
> Markus Lanthaler
> @markuslanthaler
>
>
>
>
>
Received on Tuesday, 25 March 2014 15:53:01 UTC

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