RE: defining the semantics of lists

Pat,
Re: But any triple can be in any number of graphs. If a million people are using DBpedia, then there are probably some RDF triples that in thousands of graph documents at any given moment.

Sure, the same assertion can be made in any number of graphs, but the same thing said by different parties may not be the same for the consumer – provenance matters!

We don’t “query the web” of triples, we query selected datasets/graphs on the web. Any by machine or life-form can only reason based on the information it has. OWL recognizes these dependencies with “import”. Web searches may help us find datasets/graphs – but we then choose what to trust, we close the world for our task. This is not to say all reasoning should be closed, but that we should have a choice.

Is it such a stretch then to say that we trust a graph to be complete with respect to a set of individuals having a specific class or a set of predicates having a specific property?

The general case for all the use cases I have come across is just 2 axioms:
1: Things having a specific type; that for all ?Type {?Thing a ?Type} is in graph ?G.
2: Predicates for a type; that for all ?Type, ?Predicate where {?Thing a ?Type },  {?Thing ?Predicate ?Object} is in graph ?G
So in both cases a specific triple pattern is restricted to a graph. Such graphs would be considered closed. The combination provides a lot of flexibility.
(Not a suggested syntax!)

This then allows closed-world reasoning on ?Thing and ?Predicate. I can compute an “ultimate parent”.

I am missing why this is not valuable and tractable? Combined with sub-graphs as you have proposed (perhaps micro-sub graphs for context), many RDF issues would be resolved.

-Cory

From: Patrick J Hayes <phayes@ihmc.us>
Sent: Monday, May 18, 2020 7:44 PM
To: thomas lörtsch <tl@rat.io>
Cc: Cory Casanave <cory-c@modeldriven.com>; Semantic Web <semantic-web@w3.org>
Subject: Re: defining the semantics of lists




On May 18, 2020, at 5:55 PM, thomas lörtsch <tl@rat.io<mailto:tl@rat.io>> wrote:

...

Yes, that ability – to say explicitly, in the data, that a certain set of data is complete wrt some kinds of information – would enable closed worlds to be reasoned about in an open-world reasoning framework. It is not easy to see how to do this, however. I have thought about this on and off for about a decade or more, and have not come up with a workable general way to do it.

Would very fine grained Named Graphs (*) help? Rather Named Triples that can be grouped to Graphs in arbitrary ways (virtual/nested/overlapping/fluid Named Graphs if you want). May no scale super well but let’s not do early optimization.

I do not follow what you mean here by ‘fine grained'. Named graphs would certainly help, indeed are arguably essential.

I mean defining triple per triple to what graph it belongs. That way you can have arbitrarily nested and overlapping graphs - which you’ll need when you put all sorts of information (like closedness, provenance, context etc etc) in the graph layer

? But any triple can be in any number of graphs. If a million people are using DBpedia, then there are probably some RDF triples that in thousands of graph documents at any given moment.

Pat