Entity Modelling

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

When the type of a part is identical to the type of the whole then the relationship
must be looped around to renter the top after leaving the bottom:
.
This asserts that every *type* entity is composed of one or more *type* entities... each one of which, therefore, is itself
composed of one more *type* entities ... and so on indefinitely.

The implied infinity in this model is a concern which is elaborated by Jonathon
Swift for whom the type in question is the type *flea*:

Big fleas have little fleas,
Upon their backs to bite 'em,
And little fleas have lesser fleas,
and so, ad infinitum.

In fact, if we are to avoid asserting an infinity of parts of parts of parts then
we
must specify *zero*, one or more parts within the whole as here:
. Further, if we are to avoid asserting an infinity of ever bigger conglomerates
as concerned Augustus De Morgan in his rejoinder:

And the great fleas themselves, in turn, have greater fleas to go on,
While these again have greater still, and greater still, and so on

then we must specify that a part is The example in figure 7 illustrates this looping in action; it is further developed in subsequent sections.