Re: edge attributes in JSON-LD

> On Mar 30, 2018, at 3:09 PM, Karl Grossner <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


> 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