A Noun or a Pronoun in the Possessive Case is dependent upon the Noun signifying the thing possessed.
The noun or pronoun in the possessive case is said to be governed by the noun signifying the thing possessed.
The noun governing the possessive case is often omitted.
I bought this slate at the booksellers [shop].
In such cases, supply the omission and parse according to the general rule.
In complex names and in complex titles, the sign of the possessive is put only at the end and the whole complex name or title is parsed as one word. Thus….George Washington's farewell address….not George's Washington’s.
A complex title sometimes consists of several words some of which may be different parts of speech and may have an independent construction of their own.
The captain of the guard’s horse was slain.
In parsing such a sentence OF THE GUARD should be parsed first, each word separately GUARD being in the objective. Then CAPTAIN OF THE GUARD'S should be parsed ns one complex title, in the possessive case, governed by HORSE. The ’S belongs not to GUARD but to the whole expression.
The possessive is sometimes governed by a participle used as a noun.
The cause of John's forgetting the lesson was his anxiety about the excursion.
Here….JOHN’S is in the possessive case, governed by FORGETTING used as a noun. It would not be correct to put JOHN in the objective case governed by OF. OF here, governs FORGETTING not John. The cause of John forgetting the lesson should be The cause of John's forgetting the lesson.