W3C home > Mailing lists > Public > public-linked-json@w3.org > March 2018

Re: edge attributes in JSON-LD

From: Ivan Herman <ivan@w3.org>
Date: Sat, 31 Mar 2018 08:59:15 +0200
Cc: Dan Brickley <danbri@danbri.org>, karlg <karl.geog@gmail.com>, Gregg Kellogg <gregg@greggkellogg.net>, Linked JSON <public-linked-json@w3.org>
Message-Id: <EE6D3022-AF40-461C-9AB2-98A949BC8A09@w3.org>
To: Sandro Hawke <sandro@w3.org>
Sandro, I do not have a problem with the quad/named-graph approach at all, and JSON-LD is o.k. with it. But the original request was on setting attributes to edges, which is a different ballgame…

Ivan

P.S. wary/weary… maybe it was an early morning Freudian slip :-)

> On 31 Mar 2018, at 08:19, Sandro Hawke <sandro@w3.org <mailto:sandro@w3.org>> wrote:
> 
> On 03/31/2018 01:04 AM, Ivan Herman wrote:
>> 
>> I would be very weary going down this line. We are indeed talking about, essentially, Property Graphs which is a different data model.
>> 
> 
> I think you mean "wary", but "weary" is a pretty good fit too, I bet  :-)
> 
> I haven't studied "Property Graphs" to know what their data model is, but I think what's being proposed here is perfectly reasonable to do with quads/named-graphs.  I don't find the @graph syntax nearly as readable as some other syntaxes, but the semantics are the same, and they seem entirely sufficient to me.
> 
> Yes, I know formally the semantics aren't 100.00% defined, but I'm confident they are fine in practice. If you say graph1 is valid from t1 to t2, and some triples are in graph1, it's obvious that you mean the conjunctions of those triples is valid (asserted, known to be true) from t1 to t2, and we don't really need some other formal spec to tell us that.  The one thing that's needed is the properties for valid-time-range. One could perhaps just use dc:temporal.
> 
>      -- Sandro
>> The strength of JSON-LD is that it is a serialization of RDF, thereby creating a bridge towards Linked Data. It is not the vocation of JSON-LD to redefine the underlying RDF model; by doing so, JSON-LD would depart from that connection. Closing the gap between property graphs and RDF is a perfectly justifiable discussion to have. But this discussion should not happen around JSON-LD.
>> 
>> Note that there were some attempts a few years ago to start more serious work on that at W3C but it did not happen due to lack of interest; maybe things have changed and this could be looked into again.
>> 
>> Ivan
>> 
>> 
>>> On 31 Mar 2018, at 01:17, Dan Brickley <danbri@danbri.org <mailto:danbri@danbri.org>> wrote:
>>> 
>>> At Schema.org <http://schema.org/> we can't really claim Role has worked out well. I wouldn't advocate it for this.
>>> 
>>> It would be very interesting if a syntax could be found in JSON-LD 1.1, alongwith an optional named graphs view of the data. This would help close the gap wth Property Graphs too.
>>> 
>>> Dan
>>> 
>>> On Sat, 31 Mar 2018, 00:06 karlg, <karl.geog@gmail.com <mailto:karl.geog@gmail.com>> wrote:
>>> Sub-classing schema.org <http://schema.org/> Role, e.g. with SettingRole seems promising, thanks
>>> 
>>> 
>>> kg
>>> 
>>> 
>>> {
>>> 
>>>   "@context": "http://linkedpasts.org/lp-context.jsonld <http://linkedpasts.org/lp-context.jsonld>",
>>> 
>>>   "@type": "Place",
>>> 
>>>   "name": "Abingdon",
>>> 
>>>   “properties”: {“p1”: “___”, ...}
>>> 
>>>   "setting": [
>>> 
>>>     {
>>> 
>>>       "@type": "SettingRole",
>>> 
>>>       "setting": {
>>> 
>>>         "@type": "Place",
>>> 
>>>         "name": "Berkshire"
>>> 
>>>       },
>>> 
>>>       "startDate": "1600",
>>> 
>>>       "endYear": "1974"
>>> 
>>>     },
>>> 
>>>     {
>>> 
>>>       "@type": "SettingRole",
>>> 
>>>       "setting": {
>>> 
>>>         "@type": "Place",
>>> 
>>>         "name": "Oxfordshire"
>>> 
>>>       },
>>> 
>>>       "startDate": "1974",
>>> 
>>>       "endYear": "2018"
>>> 
>>>     }
>>> 
>>>   ]
>>> 
>>> }
>>> 
>>> 
>>> On 3/30/18, 4:36 PM, "Gregg Kellogg" <gregg@greggkellogg.net <mailto:gregg@greggkellogg.net>> wrote:
>>> 
>>> 
>>> On Mar 30, 2018, at 3:09 PM, Karl Grossner <karl.geog@gmail.com <mailto:karl.geog@gmail.com>> wrote:
>>> 
>>> 
>>> Reopening this thread, as my current challenge relates closely:
>>> 
>>> I'm modeling historical Place attestations for gazetteer applications, and a potential linked.places JSON-LD modeling standard (a la linked.art). The idea is to build upon GeoJSON-LD.
>>> 
>>> Several attributes of Places are temporally indexed; i.e. may have a 'valid period', but are not amenable to event models in the same way as linked.art provenance is.
>>> 
>>> 
>>> From what I can tell, three options are @graph, n-ary relations, and rdf:Statement reification. I've rendered some sample records below. My question is whether there has emerged a best practice for this general problem of edge attributes. Any comments welcome at this stage. I have been having a conversation with @gklyne on this, here, which may (?) shed further light. https://github.com/LinkedPasts/lp-network/issues/1 <https://github.com/LinkedPasts/lp-network/issues/1>
>>> 
>>> While we could probably add something to perform reification on expansion, or transformation to RDF, it’s not clear how that would allow you to make statements about the statement, and it’s widely considered an archaic mechanism. And, it would substantially complicate the already complex API algorithms.
>>> 
>>> 
>>> The issue of edge attributes in JSON-LD is really no different than for RDF in general. While there is no syntax for automatic reification of statements, they can of course be represented in JSON-LD.
>>> 
>>> 
>>> The RDF 1.1 position is more likely that named graphs can be used for this purpose, although there are no built-in semantics. (Basically, put the statement in a named graph, and then make other meta-statements with the graph name as a subject). Your approach 01 is essentially this.
>>> 
>>> 
>>> Schema.org <http://schema.org/> takes another approach using the Role class (and sub-classes) [1], and this can be used in JSON-LD to describe information about relationships. This is what I’ve used in some of my own projects.
>>> 
>>> 
>>> Gregg
>>> 
>>> 
>>> [1] http://schema.org/Role <http://schema.org/Role>
>>> 
>>> 
>>> 
>>> thanks
>>> 
>>> --------
>>> 
>>> approach 01 (@graph; playground <https://tinyurl.com/y74p3pov> )
>>> 
>>> {
>>>   "@context": "http://linkedpasts.org/assets/place-v4-context.jsonld <http://linkedpasts.org/assets/place-v4-context.jsonld>",
>>>   "related": [
>>>     { "@id": "http://linkedpasts.org/graphs/01 <http://linkedpasts.org/graphs/01>",
>>>       "@graph": {"@id":"myplace:Abingdon","part_of":"myplace:Berkshire"},
>>>       "when": {
>>>         "timespans":
>>>             {
>>>                       "earliestYear": "1600",
>>>                       "latestYear": "1974",
>>>                       "label": "from 17c. to 1974"
>>>                     }
>>>       }
>>>     },
>>>     { "@id": "http://linkedpasts.org/graphs/02 <http://linkedpasts.org/graphs/02>",
>>>       "@graph": {"@id":"myplace:Abingdon", "part_of":"myplace:Oxfordshire"},
>>>       "when": {
>>>         "timespans":
>>>             {
>>>                       "earliestYear": "1974",
>>>                       "latestYear": "2018",
>>>                       "label": "from 1974"
>>>                     }
>>>       }
>>>     },
>>>     { "@id": "http://linkedpasts.org/graphs/03 <http://linkedpasts.org/graphs/03>",
>>>       "@graph": {"@id":"myplace:Oxford", "part_of":"myplace:Oxfordshire"},
>>>       "when": {
>>>           "timespans":
>>>             {
>>>                       "earliestYear": "1000",
>>>                       "latestYear": "2018",
>>>                       "label": "from 11c."
>>>                     }
>>>             }
>>>     }
>>>   ]
>>> }
>>> 
>>> 
>>> approach 02 (per property graph example given in this thread)
>>> 
>>> [
>>>     {"@id": "", "@type": "rdf:BoundDataset"},
>>>     {"@id": "p1", "name": "Abingdon", "type": "settlement", "_:parent_p1p3":"p3", "_:parent_p1p4":"p4"},
>>>     {"@id": "p2", "name": "Oxford", "type": "settlement", "_:parent_p2p4": "p4"},
>>>     {"@id": "p3", "name": "Berkshire", "type": "county"},
>>>     {"@id": "p4", "name": "Oxfordshire", "type": "county"},
>>>     {    "@id": "_:parent_p1p3",
>>>         "rdfs:subPropertyOf": "hasParent",
>>>         "earliestYear": 1600,
>>>         "latestYear": 1974,
>>>         "label": "from 17c. until 1974"},
>>>     {    "@id": "_:parent_p1p4",
>>>         "rdfs:subPropertyOf": "hasPparent",
>>>         "earliestYear": 1974,
>>>         "latestYear": 2018,
>>>         "label": "from 1974"},
>>>     {    "@id": "_:parent_p2p4",
>>>         "rdfs:subPropertyOf": "hasParent",
>>>         "earliestYear": 1000,
>>>         "latestYear": 2018,
>>>         "label": "from 11c."}
>>> ]
>>> 
>>> 
>>> 
>>> ----
>>> 
>>> Karl Grossner
>>> 
>>> Technical Director,
>>> World-Historical Gazetteer project for the
>>> 
>>> University of Pittsburgh World History Center
>>> 
>>> @kgeographer
>>> 
>>> Denver, CO
>>> 
>>> 
>>> 
>> 
>> 
>> ----
>> Ivan Herman, W3C
>> Publishing@W3C Technical Lead
>> Home: http://www.w3.org/People/Ivan/ <http://www.w3.org/People/Ivan/>
>> mobile: +31-641044153
>> ORCID ID: https://orcid.org/0000-0003-0782-2704 <https://orcid.org/0000-0003-0782-2704>
>> 
> 


----
Ivan Herman, W3C
Publishing@W3C Technical Lead
Home: http://www.w3.org/People/Ivan/ <http://www.w3.org/People/Ivan/>
mobile: +31-641044153
ORCID ID: https://orcid.org/0000-0003-0782-2704 <https://orcid.org/0000-0003-0782-2704>


Received on Saturday, 31 March 2018 06:59:25 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 16:18:51 UTC