Re: labelled property graphs vs -star extension of RDFn vs -star extension of named graphs

This example is similar to the ones we used in our OneGraph papers. We found no way to accommodate the "LPG way" and the "RDF way" simultaneously, without breaking RDF semantics. That's why OneGraph treats LPGs, RDF-star (as understood at the time we wrote those papers) and RDF as "lower-dimensional projections" of its graph model (that is, some information loss is possible).

I can imagine a scenario where we have two named graphs, with one :Liz :spouse :Dick triple in each, and thus those triples each get their own "edge properties". But I am reluctant to hijack named graphs for something like this, given that there are many (likely conflicting) uses of named graphs out there already. Given that named graphs have been around for quite some time already, and with no particular semantics, it would seem foolish (if not arrogant) for us to now propose one specific use for them.

My preference, for this WG, would be to stay away from named graphs altogether. My $0.02, not wearing my chair hat.

Ora

-- 
Dr. Ora Lassila 
Principal Technologist, Amazon Neptune 




On 12/8/23, 9:18 AM, "Peter F. Patel-Schneider" <pfpschneider@gmail.com <mailto:pfpschneider@gmail.com>> wrote:


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At the teleconference yesterday I mentioned that there could be user-visible
differences between different views of how to proceed, even when there is some
consensus that different views are essentially the same.


Here is one example of a user-visible divergence. Consider the following
input, written in the community group syntax.


:liz :spouse :dick {| :start 1964; :end 1974 |} .
:liz :spouse :dick {| :start 1975; :end 1976 |} .


In the community graph version of RDF-star this results in one asserted triple
with subject :liz that is the subject of four triples. In SPARQL-star, the BGP


:liz :spouse :dick {| :start 1964; :end 1976 |} .


would match against a graph constructed from this input.


In labelled property graphs this would appear to result in two asserted
triples with subject :liz, each with two property-value pairs. The above BGP
would not match.


So there is a decided visible difference between the community graph version
of RDF-star and labelled property graphs.


If I am correct in reading the (sparse) information available about RDFn, a
-star extension of RDFn would conform to the community group reading. So
there would be noticeable differences between an extended RDFn and labelled
property graphs.


I am not aware of any proposal for using named graphs that says what the above
would result in there, so it is unclear which side a named graphs version of
-star would fit into.


peter

Received on Friday, 8 December 2023 14:42:40 UTC