Why build molecules from fragments? We suppose that it
is reasonable to use molecular sub-units which have
"functional group" status in the domain of interest
(e.g., medicinal chemistry). If this is correct, the
remaining problem is to identify these fragments.
The definition of a fragment for GADD is inspired by
the definition of ClogP fragments.
ClogP fragments are defined by isolating carbons,
carbons not double or triple bonded to hetero atoms. When
ICs are removed, what's left are ClogP fragments.
For GADD, we also define "carbon fragments" as what's left
after ClogP fragments are removed.