The is_a relationship

Perhaps the most fundamental relationship is the is_a relationship. Some examples:

(grass) (is_a) (plant)

(Daniel) (is_a) (person)

This directional relationship can be used in two different contexts:

1.To indicate that one general concept builds upon another. ex. (grass) (is_a) (plant)

2.To indicate that a specific object in the world is of a certain type. ex. (Daniel) (is_a) (person)

The difference here is that (grass) is a general concept whereas (Daniel) is a real thing.