[Rdfapi-php-interest] RDQL - Confused by Inference

Hello again all,

I need some help understanding an inference query. I am confused by the
results of a query on an inference model - both forward
and backward chaining. 

In both forward and backward chaining when I use the inference model and I
send an RDQL message for a instances of a class , it also gives me instances
of a superclass. It may be because of my query - but I thought the rdf:type
would prevent that.

The behaviour I expect is that if Person is a subclass of Mammal, that if I
ask for type:Person I should get no Mammals. Conversly, if I ask for Mammals,
I should also get Persons.

Here is the RDQL:

SELECT ?Persons
WHERE (?Persons, rdf:type, ns:Person)  
USING
rdf FOR <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
ns FOR <http://newscup.net/ns#>
rdfs FOR <http://www.w3.org/2000/01/rdf-schema#>

Should I be using "find()" instead?
Apologies if this is an obvious question.