  The subsignatures of a system with continuous and exchangeable component
lifetimes form a class of indexes ranging from the Samaniego signature to the
Barlow-Proschan importance index. These indexes can be computed through
explicit linear expressions involving the values of the structure function of
the system. We show how the subsignatures can be computed more efficiently from
the reliability function of the system via identifications of variables,
differentiations, and integrations.
