[Rdfapi-php-interest] retrieving superclasses

This is an RDQL question.

I have Two classes: Mammal and Person, where Person is a subclass of Mammal.
Mammals have teeth, and Persons have the property of ProperName.

Here's the dilema. 

In RDQL, using an INFmodel I ask:
Get me all the Mammals - and it gets me the persons and mammlas correctly.
But IF I specificy that once you get me the Mammals get me the properties and
their values of people it doesn't match

For example - in this case I want all all the mammals and their properties

 WHERE   (?a, rdf:type, myns:Mammal)   ,  (?b, rdfs:domain, ?a)   

?a gives me instances of people and mammals
but using the whole RDQL above doesn't work.
Shouldn't ?b be the list of properties for at least Mammal, and maybe Persons
too?