Fluent NHibernate inheritance mapping problem

Answer 1

I'm not an expert in Fluent NH, but it seems to me that your person map should look like this:

class PersonMap : ClassMap<Person>
{
    public PersonMap()
    {  
        Id(c => c.ID).GeneratedBy.Identity();

        //this works fine
        HasMany(c => c.Pets);

        //this dosen't work, because the result contains dogs and cats
        //how can I tell NHibernate to only fetch dogs or cats?
        HasMany<Cat>(c => c.Cats);
        HasMany<Dog>(c => c.Dogs);
    }
}

Because you're Person has a Dogs property which is an IList not IList, and conversely the same for Cats.