Re: Multiple Named Graph

On 03/20/2014 04:56 PM, Reto Gmür wrote:
> Hello,
>
> I've notice that the latest published version suggest using RDF 
> formats that support multiple named graphs. For the net-worth example 
> it suggests using "one named graph for the net worth resource and then 
> two others for asset and liability containers".
>
> I am irritated by this recommendation. First the specification 
> mandates the possibility to serialize as turtle which does not 
> currently support multiple named graphs.
>
> But more importantly I don't see the reason of this splitting of the 
> information into many graphs and it seems to significantly restrict 
> the possibilities to implement LDP Servers.
>
> The suggested three graph do not seem to represent three different 
> information sources with thus potentially contradictory statements. So 
> in this situation there is typically no quotation-use case with 
> provenance that must be preserved. Grouping into different graphs what 
> can be safely expressed in one graph seems to deny the expressive 
> power of RDF and suggesting that the grouping of triples into 
> different graphs has a significance beyond provenance.
>
> With the previous published version it was possible to have an LDP 
> compliant server backed by a single graph. This would be my choice of 
> implementation if the data has a single provenance and the access 
> restrictions are the same for all the triples. This change in the new 
> version seems however to mandate implementation to be based on 
> different graphs for the different resources.
>
> In my opinion this is a significant loss of flexibility. I would like 
> for simple implementations based on one graph to be possible. It can 
> also be useful for an implementation to be based on multiple graphs 
> representing different provenances or confidentiality but containing 
> descriptions of larger and possibly overlapping sets of resources. 
> With the latter approach the resource description accessed through LDP 
> would contain more or less triples depending on my access rights and 
> the sources I've decided to trust.
>

I'm a little confused.    I see a few different options.   Can you say 
which of these you like (+1), don't mind (0), or think are harmful (-1)...?

1.  The state of every LDP-RS is really an RDF Dataset, so in addition 
to the triples you get in Turtle, if you ask for TriG, you might get a 
bunch of other data in Named Graphs

2.  Some LDP-RS's are like that, but not all

3.  None are like that.  Every LDP-RS (including every Container) has a 
state represented by exactly one RDF Graph.   Of course, you could 
represent the state of an LDP Server (which has lots of LDPR-RS's) in a 
dataset, where each LDR-RS URL was the name of a named graph containing 
that corresponding graph.

4.  Actually the entire state of some LDP Servers, with all of its 
LDP-RS's, is really just stored as one graph.   The information about 
how it is divided into LDP-RS's can be derived deterministically from 
the graph.

5.  Like 4, but this is the case of all LDP Servers.   The division of 
triples into particular LDP-RS's must never involve state that isn't 
naturally present in the one backing graph.

Having thought about this for 20 minutes now, my tentative answers would 
be 0, +1, -1, +1, -1.

       -- Sandro