Question

What is the relationsp between book and index of the book? in term of uml

Answer 1

is a relationship between classifiers which is used to show that instances of classifiers could be either linked to each other or combined logically or physically into some aggregation.
UML specification categorizes association as semantic relationship. Some other UML sources also categorize association as a structural relationship. Wikipedia states that association is instance level relationship and that associations can only be shown on class diagrams. Not sure where they got that information from but it is not based on UML specification. Association could be used on different types of UML structure diagrams:
class diagram associations,
use case diagram associations,
deployment diagram artifact associations,
deployment diagram communication path.
There are several concepts related to association:
association end ownership,
navigability,
association arity,
aggregation type.
UML 2.4 specification states that for the association: "Aggregation type, navigability, and end ownership are orthogonal concepts, ..." which is clearly an overstatement. Orthogonal usually means completely independent. While notation for aggregation type, navigability, and association end ownership could be applied independently, the concepts themselves are not orthogonal. For example, in UML 2.4 end property of association owned by an end class is navigable, which clearly makes navigability dependent on ownership.