Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and the Unified Process, Second Edition

11.4. Association Guidelines

Focus on those associations for which knowledge of the relationship needs to be preserved for some duration (“need-to-know” associations). It is more important to identify conceptual classes than to identify associations. Too many associations tend to confuse a domain model rather than illuminate it. Their discovery can be time-consuming, with marginal benefit. Avoid showing redundant or derivable associations.