One more thought: it seems like you want to dynamically cast from one type to
another. You can theoretically do that through a virtual property that points
at the instance itself but with a different declared sh:class. Add these
triples to your ontology;
hst:AAA
sh:property hst:AAA-asBBB .
hst:AAA-asBBB
a sh:PropertyShape ;
sh:path hst:asBBB ;
dash:hidden true ;
sh:class hst:BBB ;
sh:maxCount 1 ;
sh:name "as BBB" ;
sh:values [
sh:filterShape [
sh:class hst:BBB ;
] ;
sh:nodes sh:this ;
] ;
.
This computes an inferred value that has as values the focus node itself
(sh:this), but declared as BBB via sh:class. It uses a filterShape to return
null if the focus node is NOT an instance of BBB.
You can then formulate queries such as
{
aaas {
uri
asBBB {
propB
}
}
}
with an example output such as
{
"data": {
"aaas": [
{
"uri":
"http://ontology.mayo.edu/data-graphs/HierarchicalDataGraphTest#a1";,
"asBBB": null
},
{
"uri":
"http://ontology.mayo.edu/data-graphs/HierarchicalDataGraphTest#d1";,
"asBBB": null
},
{
"uri":
"http://ontology.mayo.edu/data-graphs/HierarchicalDataGraphTest#b1";,
"asBBB": {
"propB": "valueB"
}
},
{
"uri":
"http://ontology.mayo.edu/data-graphs/HierarchicalDataGraphTest#c1";,
"asBBB": {
"propB": "valueBC"
}
}
]
}
}
Note this approach already works but is a compromise:
1) It requires changes to the ontology for all cases where you want to typecast
2) It probably returns a different nesting in the result JSON (not sure)?
Does this help?
Holger
> On 28 Nov 2023, at 5:01 pm, Holger Knublauch <[email protected]> wrote:
>
>
>
>> On 28 Nov 2023, at 3:08 pm, Davide Sottara <[email protected]> wrote:
>>
>> I have put together a simple ontology with a class hierarchy, a property on
>> each class, and one individual per class - attached
>> AAA
>> DDD
>> BBB
>> CCC
>
> Thanks for the file, which I was able to play with. I also tried something
> like
>
> {
> aaas {
> uri
> ... on BBB {
> propA
> }
> }
> }
>
> but since the schema doesn't know the relationships between AAA and BBB this
> doesn't work. All types in the generated schemas are independent, no
> implements or such.
>
>>
>> I was looking for a behavior that replicates unions or interfaces:
>> https://www.apollographql.com/docs/apollo-server/schema/unions-interfaces/
>>
>> In fact, have tried setting graphql:isInterface = true, but that does not
>> seem to have any effect?
>
> graphql:isInterface is only used for round-tripping GraphQL Schema files from
> elsewhere, not those that are auto-generated.
>
> So I am afraid this syntax isn't working and you may need to revert to other
> technologies like SPARQL or ADS JavaScript to formulate such queries.
>
> Holger
>
>
>>
>> Thank you for any insight\
>> Davide
>>
>> On Wednesday, November 22, 2023 at 1:44:58 AM UTC-6 Holger Knublauch wrote:
>>> Hi Davide,
>>>
>>> thanks for the error message. I had to read up on GraphQL fragments as I
>>> have never used them.
>>> It seems that they would need to be declared using the fragment keyword but
>>> I don't see that in your query.
>>> Our GraphQL engine does not declare such fragments automatically.
>>>
>>> It would streamline this discussion if we had a complete, self-contained
>>> example.
>>>
>>> Thanks
>>> Holger
>>>
>>>
>>>
>>>> On 22 Nov 2023, at 3:59 am, Davide Sottara <[email protected] <>> wrote:
>>>>
>>>
>>>> Unfortunately I get an error
>>>> "Fragment cannot be spread here as objects of type (super) can never be of
>>>> type (sub)
>>>>
>>>> On Tuesday, November 21, 2023 at 2:55:51 PM UTC-6 Holger Knublauch wrote:
>>>>> Have you tried it out? What happened?
>>>>>
>>>>> Holger
>>>>>
>>>>>
>>>>>
>>>>>> On 21 Nov 2023, at 5:35 am, Davide Sottara <[email protected] <>> wrote:
>>>>>>
>>>>>
>>>>>> I have a class hierarchy, where the classes are also node shapes with
>>>>>> property shapes
>>>>>>
>>>>>> class AA
>>>>>> propA :String
>>>>>>
>>>>>> class BB subClassOf AA
>>>>>> propB : String
>>>>>>
>>>>>> Is a query like the following supported?
>>>>>>
>>>>>> aaas {
>>>>>> propA
>>>>>> ... on bbb {
>>>>>> propB
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> Thank you
>>>>>>
>>>>>
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>>>>
>>>>
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>>>
>>
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>> <HierarchicalDataGraphTest.trig>
>
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