Object-oriented inheritance has been in widespread use for a decade, 
and it is now realised that although inheritance 
is a powerful modelling tool with many associated advantages, 
its benefits are not automatically conferred on systems that simply use it. 
This book introduces a model of inheritance based around 
five fundamental inheritance relationships. 
Each relationship has a clear conceptual basis, 
representing a fundamental, specialised use of inheritance. 
The resulting model replaces a confused notion of inheritance 
with five distinct conceptual relationships 
supporting more precise modelling of systems 
and capturing the semantic intent of each use of inheritance within a system.