does not understand (1) OOV words, e.g., "the opposite wall" * ; (2) more than one meaning of polysemous positional relations, e.g., "to the left of the table" * as "to the left and on the table" as well as "to the left and next to the table"; (3) positional relations that are complex, e.g., "in the left near corner of the table" * , or don't have a landmark, e.g., "the ball in the center" * ; and (4) descriptive prepositional phrases starting with "of" or "with", e.g., "the picture of the face" * and "the plant with the leaves" * .
contextual information sometimes enables the system to overcome OOV words.