Querying polymorphism in RDF database using SPARQL - sparql

Question

I have a question about polymorphism in RDF schema.
I created a class "MobilePhone":
#prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
#prefix schema: <http://schema.org/> .
#prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
#prefix my: <http://localhost/> .
my:MobilePhone rdf:type rdfs:Class .
my:MobilePhone rdfs:subClassOf schema:Product .
my:MobilePhone rdfs:label "MobilePhone" .
Then I executed two queries:
PREFIX : <http://schema.org/>
PREFIX my: <http://localhost/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?instance
WHERE {
?instance a my:MobilePhone .
}
and
PREFIX : <http://schema.org/>
PREFIX my: <http://localhost/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?instance
WHERE {
?instance a :Product .
}
I expected the second query to retrieve all Products. Even "MobilePhone" products. But that didn't happen. I had to use:
PREFIX : <http://schema.org/>
PREFIX my: <http://localhost/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?instance
WHERE {
?class rdfs:subClassOf* :Product .
?instance rdf:type ?class .
}
Does anyone know if it is possible to update my schema so the first query for searching all Products would work?

Answer 1

It is possible to update your data (not your schema [or ontology]) to deliver the desired result, by "forward chaining" -- i.e., by explicitly including statements that each entity which is a my:MobilePhone is also a :Product.
It's also possible to use "backward chaining" to deliver the desired result; the specifics of this will vary with your triple/quad store and other software. (My employer's solution, Virtuoso, uses a DEFINE input:inference pragma to activate an inference rule set for each query.)
Both of these may be considered as "inferencing" or "reasoning", though common usage generally applies these terms only to the dynamic action -- which happens with every query in "backward chaining", and once, pre-query, typically during data load, in "forward chaining".