The functional size of a system may change as a result of the
enhancement. The size after
enhancement can be calculated by analysing
the whole application anew or by
taking account of
the changes from the
original FPA analysis. Steps to take are:
-
Calculate the function point size of the application prior to the
change (FP
BASE
) using the
standard FPA method.
-
Identify the transactional and data functions deleted from the
existing application and
determine their function point size (Σ
FP
DELETED
).
-
Determine the transactional and data functions changed. Calculate
the number of function
points these represent before and after the
enhancement (Σ FP
AFTER
and Σ FP
BEFORE
), using the
standard FPA method.
-
Determine the transactional and data functions added to the
system
and calculate how many
function points these represent (Σ FP
ADDED
).
-
Calculate the size of the system after enhancement (FP
NEW
).
FP
NEW
= FP
BASE
+ (Σ FP
ADDED
)
+ (Σ FP
AFTER-CHANGE
- Σ FP
BEFORE-CHANGE
)
- (Σ FP
DELETED
)
Note: the Impact Factor does not play when determining the size of the
system after enhancement.