Chaining and mixing of supertype-subtype and type-instance relationships

Hi there,

I have been thinking about the chaining and mixing of supertype-subtype 
(sub - transitive) and type-instance (isa - not transitive) 
relationships - and would like to verify my assumptions.

Assume the following example:

E sub D isa C sub B sub A

->

1) D is an instance of B and A (due to transitivity in "C sub B sub A")
2) E is an instance of C, B, and A (due to transitivity in "E sub D" and 
"C sub B sub A")

I found this in the latest TMRM draft in 5b) [1]:

"[...] Additionally, whenever a proxy a is an instance of another c, 
then a is an instance of any superclass of c: if x isa,m c and c sub,m 
c' , then x isa,m c' is true."

This supports 1), however I did not find any notes in the standards 
supporting 2).

What do you think?

Best regards,
Johannes

[1] http://www.isotopicmaps.org/TMRM/TMRM-7.0/tmrm7.pdf