Fw: Multiple Named Graph

From:   Reto Gmür <reto@apache.org>
To:     "public-ldp@w3.org" <public-ldp@w3.org>, public-ldp-wg@w3.org, 
Date:   03/20/2014 06:56 AM
Subject:        Multiple Named Graph



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.

Cheers,
Reto