Formulas are just sets of triples, so we can test for what is not contained.

If someone's page does not say they are vegetarian, let's assume they are an omnivore:

this log:forAll :x.
{:x :homePage log:notIncludes 
                  { :x a :Vegetarian }}
=> { :x a :Omnivore }. 

Of course, using defaults like this often gives wrong results

...but sometimes it's still your best option.