af Olivier Costa 11 år siden
168
Mere som dette
Kanban
WIP limits
scrum
timeboxing
quickly & aggressively
to make correction matter
only usefull when having cummulative invariants
as IS the case in product development
previous phases influence following phazes
as is NOT the case in manufactoring
effects of invariants are 'reset' between states
in test with
other outcomes (fuzzy)
simply put
maximize probality over all results
3 possible results
33% probality
more complex
binary outcome
true/false
maximul efficiency is reached when probability on true or false = 50%
snow in july in los angeles
near 0 %
snow in dec in denmark
near 100%
why ?
modules often too toghtly coupled
DDD
information radiators
but not cost !
show size
don't see the queues
it's information
stocked in inventories
don't know that
planning with 98,5 % usage
only work in a deterministic world
which we are nog living in
is the cause of so much of the delays and unpredictability they encounter
know that
keeping 10-15% slack is needed
to be able to meet expected delvery dates
queue size goes up exponentially when nearing 100% usage
breakeven
around 85% - 90% usage
cost of queue size
aount of unfinished work
cost of 'slack'
not using 100% of the queues
on unproductive threads
or paths that you can abandon
now change the pay-off function
nothing else has changed
but cost reduced significantly
buy digit for 1€
cost of 3 digit nr is now (on average) 1,11 €
buy 2nd & 3d digit after getting feedback
lotery:
buy number
for 3 €
1 chance in 1000 to win
1 chance in 1000 to pick winning 3 digit number
earning 3000 €
reduce queues
aka unfinished Work in Progress
minimize lead-time
maximize flow
set WIP limits
aka inventories
in manufactoring world
smaller batch sizes
iterations of weeks rather than quarters or years
eg: using spelling checker
eg: prefect speller & typist
is under our control
needs to be assymetric
which is the case in development
