Bi-directional association between Footballer Mapper and Bowler Mapper

This question is about a specific UML diagram in the book called Patterns Of Enterprise Application Architecture, by Martin Fowler.

Wh开发者_如何学编程y is there a 'bi-directional association' between Footballer Mapper and Bowler Mapper in the 'Inheritance Mapper' Class Diagram on page 302?

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There isn't.

You're looking at an aggregation from the Player Mapper to one of the concrete mappers: Footballer Mapper, Bowler Mapper and Cricketer Mapper.

If you read the 2nd paragraph on page 304, he explains this design choice.