W3C home > Mailing lists > Public > public-lod@w3.org > September 2011

Re: Minimum useful linked data

From: Dave Reynolds <dave.e.reynolds@gmail.com>
Date: Sat, 03 Sep 2011 19:15:01 +0100
To: linked-data-api-discuss@googlegroups.com
Cc: public-linked-json@w3.org, public-lod@w3.org
Message-ID: <1315073701.2924.36.camel@Obsidian3>
[Left dist list in place but seems a little broad.]

Hi Danny,

On Sat, 2011-09-03 at 19:34 +0200, Danny Ayers wrote: 
> 
> On the other hand the linked data API has this covered, e.g. in the
> deployment example [2]:
> 
>      /doc/school/12345 should respond with a document that includes
> information about /id/school/12345 (a concise bounded description of
> that resource)
> 
> Except that to work with a CBD, reasonable knowledge is needed of RDF
> *and* there isn't really a friendly mapping from arbitrary graphs to
> JSON.

Actually a developer doesn't need to know anything about CBD for the
Linked Data API (LDA). 

The person who defines the Linked Data API spec for a given endpoint
does need to understand RDF but the consumer can work purely with
developer friendly JSON or (non-namespace) XML..

In fact most API endpoints define views of subsets of properties [3],
though a "describe" view is always available. What's more Jeni's style
sheet for data.gov.uk provides nice HTML browsing of the views available
from the end point automatically generated from the LDA metadata, see
[4] for instance.

If you select the "all" view (which is a complete Describe and select
JSON then you see [5]. Apart from there being a heck of a lot of
properties in that data I don't think the resulting JSON is too bad and
the default view [6] is really quite usable.

> But surely most of the immediately useful information (and ways to
> find further information) about the resource </doc/school/12345> will
> be contained in the triples matching:
> 
> </doc/school/12345> ?pA ?o .
> ?s ?pB </doc/school/12345> .
> 
> where ?o and ?s *are not bnodes*

Yes in the Linked Data API you can specify this and select the limited
sets of p's for each view. We did find we need to be able to selectively
pull back deeper nested structure to make the JSON API usable. The most
common case being labels on resources but we also have cases like vcard
where you want to pull back substructure. See the address part of [6]
for example. That way the person who specifies the LDA for a given
dataset can create nice self contained views of the data includes nested
structures so that the consumer just has the traverse the JSON and not
have the manually walk a load of links just to get one logical record.

Cheers,
Dave

[3] http://code.google.com/p/linked-data-api/wiki/API_Viewing_Resources
[4] http://education.data.gov.uk/doc/school/100866
[5] http://education.data.gov.uk/doc/school/100866.json?_view=all
[6] http://education.data.gov.uk/doc/school/100866.json
Received on Saturday, 3 September 2011 18:16:02 UTC

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