- From: Olaf Hartig <olaf.hartig@liu.se>
- Date: Thu, 19 Sep 2019 10:46:12 +0000
- To: Jeff Lerman <jeff.lerman@invitae.com>
- CC: "public-rdf-star@w3.org" <public-rdf-star@w3.org>
Hi Jeff, On Fri, 2019-08-30 at 11:56 -0700, Jeff Lerman wrote: > Ah, that’s more in-line with much of the other discussion so far in > the group. > > I would prefer a model in which it’s not possible to assert a > property on a non-existent edge. We have just started a discussion related to this question in another thread (PG mode and SA mode). It would be nice if you could elaborate on this preference over there! > [...] > I have more to say about ways to handle/leverage named graphs, which > might make my 2nd suggestion more palatable, but not sure that this > is the right forum for that. I think there are other more suitable forums to have discussions specific to named graphs (unless the topic is also related to the RDF*/SPARQL* approach). Best regards, Olaf > If the extension I have in mind would solve this issue with RDF* > though, maybe it is... > > Jeff LermanAI ScientistMobile: 510-495-4621www.invitae.com > > > On Fri, Aug 30, 2019 at 11:23 AM Olaf Hartig <olaf.hartig@liu.se> > wrote: > > Jeff, > > > > These are great examples for cases in which the properties > > associated with edges in a graph may change over time without > > affecting the existence of the edges themselves. However, I think > > Pierre-Antoine's question was focusing on the opposite: does the > > existence of an edge property always assume the existence of the > > edge with which it is associated. > > > > Olaf > > > > -----Original Message----- > > From: Jeff Lerman <jeff.lerman@invitae.com> > > To: Joshua Shinavier <joshsh@uber.com> > > Cc: Pierre-Antoine Champin <pierre-antoine.champin@univ-lyon1.fr>, > > public-rdf-star@w3.org > > Sent: Fri, 30 Aug 2019 18:27 > > Subject: Re: do Property Graphs always assert annotated arcs? > > > > Hi all, > > > > Most of my experience with graphs is with a frame-based approach > > that most > > closely resembles a triple-store - not explicitly RDF but close > > enough. > > I’ve been exploring both RDF/triple-stores and PGs as candidates to > > support > > a new project. I’ve been following the RDF* discussion with > > interest. > > > > For what it's worth, I wouldn’t assume that edge-metadata (edge- > > properties > > in PG world) must be asserted at the time an edge is asserted. > > There are a > > variety of scenarios in which one might wish to update that > > metadata, and > > I’m pretty sure there’s nothing technically preventing such updates > > in > > existing PG implementations. For example, one might: > > > > - update metadata: alter the value of an already-asserted > > property:value > > pair (e.g., a newer model indicates that the weight of an edge > > should be > > adjusted from 0.2 to 0.8) > > - add or subtract metadata: assert (or remove) a value for a > > property > > that was previously un-populated (or populated), to reflect new > > knowledge > > we have about a relationship. The change could be incremental > > and need not > > affect other properties, so deleting-and-reasserting the edge > > with all of > > the other pre-existing (and unaffected) properties would be > > inappropriate. > > > > —Jeff > > > > > > > > [image: email_sig_logo_vert.png] > > > > Jeff Lerman > > > > AI Scientist > > > > Mobile: 510-495-4621 > > > > www.invitae.com > > > > [image: email_sig_social_linkedin.png] > > <https://www.linkedin.com/in/jefflerman/> > > > > > > On Thu, Aug 29, 2019 at 10:03 AM Joshua Shinavier <joshsh@uber.com> > > wrote: > > > > > Hi Pierre, > > > > > > Just a quick response from a representative "property graph" > > user. I have > > > not been active on this list so far, and actually mistook your > > email for a > > > gremlin-users post. So let me just say what I would have said. > > > > > > First of all, property graph frameworks are usually not > > prescriptive about > > > semantics, so your property-qualified edge "means what you want > > it to > > > mean". At the same time, it is generally not the case that an > > edge > > > qualified with a property like "since" would be considered to be > > asserted, > > > independently of the property. A canonical example is the > > TinkerPop toy > > > graph > > > < > > http://tinkerpop.apache.org/docs/current/reference/#graph-computing > > >, > > > which has a "weight" property on each edge. The edge > > created{peter, lop} > > > has a weight of 0.2, which basically means that the statement > > "Peter is a > > > creator of LOP" is a non-assertion. I read your :since and :until > > example > > > exactly as you do: the statement spouse{alice, bob} is asserted > > > conditionally on a logical point in time. > > > > > > Josh > > > > > > > > > On Thu, Aug 29, 2019 at 8:36 AM Pierre-Antoine Champin < > > > pierre-antoine.champin@univ-lyon1.fr> wrote: > > > > > >> Hi all, > > >> > > >> here is a question for those on the list who have discussed more > > than I > > >> have with Property Graph users. > > >> > > >> There seem to be a consensus here that in PG, arcs with metadata > > are > > >> asserted at the same time as they are annotated. This is > > reflected in the > > >> PG interpretation of RDF*, where: > > >> > > >> <<:alice :spouse :bob>> :since 2001-02-03^^xsd:date . > > >> > > >> asserts exactly two triples. > > >> > > >> But as I understand, PG people are also likely to express things > > like: > > >> > > >> <<:alice :spouse :bob>> :since 2001-02-03^^xsd:date ; > > >> :until 2004-05-06^^xsd:date . > > >> > > >> if Alice and Bob eventually got divorced. > > >> In that situation, the arc <<:alice :spouse :bob>> should *no > > longer* be > > >> considered asserted in the graph. > > >> > > >> Question: is this scenario a plausible one in a PG context? > > >> > > >
Received on Thursday, 19 September 2019 10:47:01 UTC