THE PREPOSITION de IN GLOSA MEANS "OF," "BELONGING TO," OR "ABOUT." U bibli de Petro CAN MEAN "PETRO'S BOOK" OR "THE BOOK ABOUT PETRO." HOW CAN A LOGICAL LANGUAGE TOLERATE SUCH AMBIGUITY?
Short answer: Many natural languages have different meanings for the word DE. They are not in danger of collapsing.
First of all, why shouldn't speakers of the above languages have a preposition that is easy for them to use?
Glosa does have ways of expressing the two meanings precisely:
U bibli; Petro habe...
The book Petro owns...
U tema de u-la bibli es de Petro.
The theme of the book is about Petro.
U bibli tema de Petro.
The book "themes" about Petro.
(TEMA is used as a verb.)
U bibli es tema Petro.
The book is about Petro.
(TEMA is used as a preposition.)