container


In Deriscope terminology, a
Deriscope Type A is called a container of a type B if A contains B, in the following sense:
Every object of B is also an object of A, but not vice-versa.

It follows that then B is a
subtype of A

As an example, the following three statements hold:
1) The type
Tradable is a container of the type Bond
2) The type
Tradable is also a container of the type Zero Bond
but
3) The type
Tradable is not a container of the type Tradable