SPARQL: Get "most specific property"

I'm trying to fetch the most specific properties for a class, and I'm stuck. I want to pull out all the properties that apply for a given class (including those inherited from superclasses), except those properties that have subproperties in the result set.

For example, if I have a class Population with one of its properties being atLocation, and a subclass of Population called Refugees. Refugees has a property currentLocation, which is a subProperty of atLocation.

So what I want is a generic query that would give me only atLocation if I put in Population, and only currentLocation if I put in Refugees. What I have is this:

prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
prefix ex: <http://example.org/vocabulary#>

SELECT DISTINCT ?prop WHERE {
  ex:Refugee rdfs:subClassOf* ?domain  .
  ?prop rdfs:domain ?domain .
  ?subprop rdfs:domain ?domain .
  FILTER NOT EXISTS { ?subprop rdfs:subPropertyOf ?prop . }  
} ORDER BY ?prop

This gives me both atLocation and currentLocation, though.

Is this possible in one query at all? Any ideas on how to solve this appreciated!

Solution

This was trickier than I anticipated when I tried it for myself. However, what you need to do is extend your NOT EXISTS clause somewhat.

SELECT ?prop WHERE {
  ?prop rdfs:domain ?domain .
  ?class rdfs:subClassOf* ?domain .
  FILTER NOT EXISTS {
        ?sub rdfs:subPropertyOf ?prop.
        ?sub rdfs:domain ?d.
        ?class rdfs:subClassOf* ?d .
  }
  FILTER (?class = ex:Refugee)
}

We're selecting all properties whose domain is ex:Refugee or a superclass of ex:Refugee (first two BGPs). But then we want to filter out those properties for which a subProperty exists that also has a domain which is (a superclass of) ex:Refugee. Note that we are using a different variable for the domain of the sub-property (?d), after all it does not necessarily have to have the exact same domain as the property we are selecting.

The above works on a simple (non-entailment or RDF(S) entailment) triplestore, provided each sub-property only has its most specific domain class defined, that is, you have the triple 'ex:currentLocation rdfs:domain ex:Refugee' but not explicitly 'ex:currentLocation rdfs:domain ex:Population'.