In Deriscope terminology, a Deriscope Type B is called a subtype of a type A if B is contained in A, in the following sense:
Every object of B is also an object of A, but not vice-versa.
It follows that then A is a container of B
As an example, the following three statements hold:
1) The type Bond is a subtype of the type Tradable
2) The type Zero Bond is also a subtype of the type Tradable
3) The type Tradable is not a subtype of the type Tradable