RE: Understanding linked data fragments

Hi Nathan,

Welcome on board.


On Thursday, February 05, 2015 5:29 AM, Nathan Ridley wrote:
> I'm working on a project in which JSON-LD and Hydra have been selected
> as key aspects of the project's architecture and implementation. I've

That's fantastic. Can you already share some more details about that project?


> been tasked with researching a number of areas to better understand
> how JSON-LD and Hydra are to be correctly made use of, and a picture
> is slowly starting to form regarding how all of this fits together.

Yeah, we could do a better job at giving a high-level overview of how all of this ties together. It would be terrific if you happen to write something like that and are able to share it. Doesn't need to be anything formal. I'm sure we'll find the right place for it :-)


> One thing that is currently unclear to me, despite having read the
> specs multiple times, is exactly what problem "Linked Data Fragments"
> are solving, other than to simply provide a standardized hypermedia-
> enabled grouping format for a subset of returned data, its metadata
> and hypermedia controls.

As Ruben already explained, that's basically it. The idea is to restrict the query interface as much as possible to make it very easy to answer the queries. Triple Pattern Fragments, currently the only "implementation" of Linked Data Fragments allow you to query by any combination of subject, predicate, and object. So, every triple in your data store can appear in a maximum of 2³ queries:

   The triple "a b c", e.g., will be returned for these queries
   (where ? is a wildcard that accepts any value):
      a b c
      a b ?
      a ? c
      a ? ?
      ? b c
      ? b ?
      ? ? c
      ? ? ?

The idea then is to fetch at least data as possible from the server—which is being enabled by the triple count in the metadata—and perform the actual SPARQL query locally.


 
> If my question is too large, I'm not out to waste anybody's time - even
> a pointer to an article, blog post or other publication that answers my
> question would be appreciated.

This questions are extremely valuable as they help us to improve what we have and see what "newcomers" are struggling with. Unfortunately, it's easy to get blind for these issues after having worked on something for a while.

Btw. I see you haven't joined the Hydra W3C Community Group yet. Could you please do so. The necessary steps are described at

   http://www.hydra-cg.com/#community


Thanks,
Markus


--
Markus Lanthaler
@markuslanthaler

Received on Thursday, 5 February 2015 21:28:37 UTC