Entity Modelling

www.entitymodelling.org - entity modelling introduced from first principles - relational database design theory and practice - dependent type theory


The existence and ownership of particular phone numbers may be communicated or stored independently in which case they have the message structure:

particular_phone_number => phone number,
The world as a whole now is communicated as :
world => person*,
person => name,
data of birth
particular_phone_number => phone number,

This world view given by the message scheme (11) is an example of a relational schema. In summary, we have two possible ways of describing the world view in messages, the relational one (11) and the hierarchic1 one shown in full in (12).

world => person*
person => name,
data of birth,
phone number*

1In this context, the term hierarchical and the term relational are generally used as contrasting terms but in actual fact a relational schema can be seen to be a special case of a hierarchical schema — one in which the hierarchical structure is minimised.