Edge property example error

Support
1

I am looking at this blog post Property Graphs meet Stardog | Stardog
and would like to write these triples to a database:

:Alice :worksFor {:role :CEO ;  
                  :since 2010 ;
                  :probability 0.8 ;
                  :source <http://example.com/news>} :ACME ;
       :birthDate {:probability 0.2} "1972-01-01"^^xsd:date ;
       :nationality {:source <http://example.org/Alice>} :USA .

However I am getting this error when executing:

QE0PE2: com.complexible.stardog.plan.eval.ExecutionException: Encountered " <PNAME_LN> ":Alice "" at line 1, column 1.
Was expecting one of:
    <EOF> 
    ";" ...
    <HINT> ...

any idea?

2

Never mind - I have created a new database with `edge.properties=true - and adding the above ttl worked.

Two more questions:

  1. When I go to visualize Alice node I see worksFor edge but no edge properties can be displayed. Do you plan to add this?
  2. When I "Run to File" the visualization and export it to JSON-LD I don't get any edge properties.
  3. Do you plan to make edge properties exportable and importable to and from JSON-LD?

Here is the exported JSON-LD - and no edge properties:

[ {
  "@id" : "http://api.stardog.com/Alice",
  "http://api.stardog.com/birthDate" : [ {
    "@type" : "http://www.w3.org/2001/XMLSchema#date",
    "@value" : "1972-01-01"
  } ],
  "http://api.stardog.com/nationality" : [ {
    "@id" : "http://api.stardog.com/USA"
  } ],
  "http://api.stardog.com/worksFor" : [ {
    "@id" : "http://api.stardog.com/ACME"
  } ]
} ]
3

Hi Radu,

Our JSON-LD parsers and serialisers already support edge properties. That's easy to verify by running something like

construct { << :Alice ?p ?o >> ?ep ?epv } {
  << :Alice ?p ?o >> ?ep ?epv
}

you'll see the returned edge properties (eg. in Studio, which uses JSON-LD exclusively at this time). And you'll even see the edge properties in the viz, if you visualise that. You'd need to additionally toggle "Literals as nodes" in the Options menu in the bottom right corner.

What you observe isn't a JSON-LD, viz, or even Studio limitation, it's simply that DESCRIBE queries (used explicitly or implicitly) don't yet return edge properties. And yes, there's a ticket to resolve that (also, Stardog allows users add custom DESCRIBE strategies: stardog-examples/examples/describe at develop · stardog-union/stardog-examples · GitHub).

Best,
Pavel

4

Pavel - thank you for your response.

I can see edge properties visualization in Studio.

And I was able to export the following JSON-LD:

[ {
  "@id" : {
    "@id" : "http://api.stardog.com/Alice",
    "http://api.stardog.com/birthDate" : {
      "@value" : "1972-01-01",
      "@type" : "http://www.w3.org/2001/XMLSchema#date"
    }
  },
  "http://api.stardog.com/probability" : [ {
    "@type" : "http://www.w3.org/2001/XMLSchema#decimal",
    "@value" : "0.2"
  } ]
}, {
  "@id" : {
    "@id" : "http://api.stardog.com/Alice",
    "http://api.stardog.com/nationality" : {
      "@id" : "http://api.stardog.com/USA"
    }
  },
  "http://api.stardog.com/source" : [ {
    "@id" : "http://example.org/Alice"
  } ]
}, {
  "@id" : {
    "@id" : "http://api.stardog.com/Alice",
    "http://api.stardog.com/worksFor" : {
      "@id" : "http://api.stardog.com/ACME"
    }
  },
  "http://api.stardog.com/probability" : [ {
    "@type" : "http://www.w3.org/2001/XMLSchema#decimal",
    "@value" : "0.8"
  } ],
  "http://api.stardog.com/role" : [ {
    "@id" : "http://api.stardog.com/CEO"
  } ],
  "http://api.stardog.com/since" : [ {
    "@type" : "http://www.w3.org/2001/XMLSchema#integer",
    "@value" : "2010"
  } ],
  "http://api.stardog.com/source" : [ {
    "@id" : "http://example.com/news"
  } ]
} ]

However when I try to import the json LD via HTTP POST api call I get the following error:

400 {"message":"Could not parse JSONLD: invalid @id value: value of @id must be a string","code":"QEIVR2"} b'{"message":"Could not parse JSONLD: invalid @id value: value of @id must be a string","code":"QEIVR2"}'
400
5

@pavel thanks for trying to help over this long weekend.

What I really need is an example of JSON-LD that can imported demonstrating how to add edge properties.

  • Can you please provide such an example?

Thanks,
Radu

6

Radu,

My apologies for the delay on this. Indeed I confirm that the JSON-LD parser has issues with edge properties at the moment. I created an issue # 9301 for this and we intend to look into it ASAP.

Thanks for bringing this up,
Pavel

7

Thank you @pavel - looking forward to the fix