for G being non empty RelStr
for H1, H2 being RelStr st the carrier of H1 misses the carrier of H2 & ( RelStr(# the carrier of G, the InternalRel of G #) = union_of (H1,H2) or RelStr(# the carrier of G, the InternalRel of G #) = sum_of (H1,H2) ) holds
( H1 is full SubRelStr of G & H2 is full SubRelStr of G )