has_a: Properties VS possessions

As I was working on an implementation for exercise 3 tonight, I realized that there is a difference between has_a in the sense of a property VS has_a in terms of a "possession".

Example of a property:

Daniel has_a nose

Example of a possession:

Daniel has_a dog

Where this difference comes into play is in the implementation of the HasA function, and can be highlighted by the following:

Test case 1:

Daniel has_a human_body
human_body has_a human_head
human_head has_a nose

The property Daniel.nose makes sense because each of the above has_a relationships describe properties, or parts.

Test case 2:

Daniel has_a dog
dog has_a tail

The property Daniel.tail doesn't make sense because the relationship Daniel has_a dog is describing dog as a possession of Daniel, rather than as a property.