Re: Learning JSON-LD - some questions

Hello Ivan,

Thank you for your quick reply. It was useful.

Your point regarding

     "task:taskDescription": {
                "@value": "The description of the task"
        },

vs

     "task:taskDescription": "The description of the task",

is well taken.

It does bring up another question.

Let's say that I had:

{
    "@context": {
        "tt": "http://my-company-name/Tasking#",
        "task": "http://my-company-name/data/TaskingOntology#"
    },
    "@graph": [
        {
            "@id": "tt:taskparta_TaskSubject",
            "task:enumerated": {
                "@id": "tt:taskEnum"
            }
        }
    ]
}

In this case, tt:taskEnum can be correctly expanded to
http://my-company-name/Tasking#

However, if I did "task:enumerated": "tt:taskEnum", then it would not be
expanded.

I am just trying to understand the expansion rules a bit better. Is there
anything you would be able to say to help me understand the expansion rules?

But, this may be a case of needing to read the spec (RTFM). It may help if
there was a particular part of the spec that speaks directly to this issue.

Regards,
James

On Sat, Mar 7, 2020 at 3:02 AM Ivan Herman <ivan@w3.org> wrote:

> Dear James,
>
> First of all, to your second and third question: the JSON-LD you have is
> absolutely correct and, without knowing the details of the vocabulary you
> use, does not 'smell':-). As for the 'a' in the turtle output, that is a
> widely used Turtle idiom (does not have anything to do with JSON-LD: it is
> a shorthand for rdf:type.
>
> I have made a few changes on your example, mostly to address your first
> question. The "@graph" construct makes it possible to gather nodes on the
> 'top level' as you wanted but also to share contexts. Ie, you do not have
> to repeat the context. The other change I have made is when you have
> properties whose values are simply strings, it is possible to make the
> JSON-LD data more compact by just using that string as a value. Though your
> construction of using an object with "@value" is absolutely correct, it is
> too complicated for that simple case.
>
> Here is the new version:
>
> {
>     "@context": {
>         "tt": "http://my-company-name/Tasking#",
>         "task": "http://my-company-name/data/TaskingOntology#",
>         "rdfs": "http://www.w3.org/2000/01/rdf-schema#"
>     },
>     "@graph": [
>         {
>             "@id": "tt:Task_3",
>             "@type": "task:Task",
>             "task:itemToTeardown": {
>                     "@id": "tt:TaskSubject"
>             },
>             "task:taskDescription": "The description of the task",
>             "rdfs:label": "Task 3"
>         },
>         {
>             "@id": "tt:taskparta_TaskSubject",
>             "task:isComponentOf": {
>                     "@id": "task:TaskSubject"
>             },
>             "rdfs:label": "Label A"
>         },
>         {
>             "@id": "tt:taskpartb_TaskSubject",
>             "task:isComponentOf": {
>                     "@id": "task:TaskSubject"
>             },
>             "rdfs:label": "Label B"
>         }
>     ]
> }
>
> I hope this helps
>
> Sincerely
>
> Ivan Herman
>
>
>
>
>
> On 6 Mar 2020, at 19:22, James Hudson <jameshudson3010@gmail.com> wrote:
>
> I have the following JSON-LD document:
>
> [
>     {
>         "@context": {
>             "tt": "http://my-company-name/Tasking#",
>             "task": "http://my-company-name/data/TaskingOntology#",
>             "rdfs": "http://www.w3.org/2000/01/rdf-schema#"
>         },
>         "@id": "tt:Task_3",
>         "@type": "task:Task",
>         "task:itemToTeardown": {
>                 "@id": "tt:TaskSubject"
>         },
>         "task:taskDescription": {
>                 "@value": "The description of the task"
>         },
>         "rdfs:label": {
>                 "@value": "Task 3"
>         }
>     },
>     {
>         "@context": {
>             "tt": "http://my-company-name/Tasking#",
>             "task": "http://my-company-name/data/TaskingOntology#",
>             "rdfs": "http://www.w3.org/2000/01/rdf-schema#"
>         },
>         "@id": "tt:taskparta_TaskSubject",
>         "task:isComponentOf": {
>                 "@id": "task:TaskSubject"
>         },
>         "rdfs:label": {
>                 "@value": "Label A"
>         }
>     },
>     {
>         "@context": {
>             "tt": "http://my-company-name/Tasking#",
>             "task": "http://my-company-name/data/TaskingOntology#",
>             "rdfs": "http://www.w3.org/2000/01/rdf-schema#"
>         },
>         "@id": "tt:taskpartb_TaskSubject",
>         "task:isComponentOf": {
>                 "@id": "task:TaskSubject"
>         },
>         "rdfs:label": {
>                 "@value": "Label B"
>         }
>     }
> ]
>
>
> using https://github.com/RDFLib/rdflib-jsonld, it will produce the
> following RDF:
>
> @prefix ns1: <http://my-company-name/data/TaskingOntology#> .
>
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
>
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
>
> @prefix xml: <http://www.w3.org/XML/1998/namespace> .
>
> @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
>
>
> <http://my-company-name/Tasking#Task_3> a ns1:Task ;
>
>     rdfs:label "Task 3" ;
>
>     ns1:itemToTeardown <http://my-company-name/Tasking#TaskSubject> ;
>
>     ns1:taskDescription "The description of the task" .
>
>
> <http://my-company-name/Tasking#taskparta_TaskSubject> rdfs:label "Label A" ;
>
>     ns1:isComponentOf ns1:TaskSubject .
>
>
> <http://my-company-name/Tasking#taskpartb_TaskSubject> rdfs:label "Label B" ;
>
>     ns1:isComponentOf ns1:TaskSubject .
>
>
> I have the following questions:
>
> (1) I need to duplicate the @context across several entries. Is there some
> way to avoid that? I note that in the RDF, the common prefixes can be
> shared.
>
> (2) Does the JSON-LD stuff look "right"? Does anything smell? It is hard
> for me to judge having only starting looking at such things.
>
> (3) In the RDF, I see <http://my-company-name/Tasking#Task_3> *a*
> ns1:Task ; ... what is the 'a'? Where did it come from?
>
> Thank you.
>
>
>
>
>
>
>
>
>
>
> ----
> Ivan Herman, W3C
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> ORCID ID: https://orcid.org/0000-0003-0782-2704
>
>