container type
In Deriscope terminology, a Deriscope TypeA is called a container type 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 type of the type Bond
2) The type Tradable is also a container type of the type Zero Bond
but
3) The type Tradable is not a container type of the type Tradable