I hardly see how you can define in a RDBMS that a resource that both have an engine and four wheels should be seen as a car.
Without going into a nightmare of unbearable SQL...
The SQL for describing "resources that contain other resources" gets a bit unidiomatic, but defining a query for those that have e.g. an engine and four wheels is quite easy. Then you can add that as a custom view, so that your inferred data is in turn available and queryable on an equal basis with raw input to the knowledge base.
Sure. But maintaining the coherence between your business data model definitions and their implementation in the RDBMS can quickly become a massive headache, don't you think?