RE: SIP is not Takt Time

Kent,

On Monday, 3 February 2003 4:39 PM, Kent Beck 
[SMTP:[email protected]] wrote:
>
> >In many other respects I agree with your sentiments about SIP. It is a
> >vital metric for Agile processes. However, in Lean, Inventory takes
> >second place to Value. With XP you always pushed working code as the
> >indicator of delivered value. I think you should stick with that as
> >the most important metric for Agile. Value is #1. Inventory is #2.
> >Takt Time (your current SIP) is #3 (though it is related to both Value
> >and Inventory). Last would be Operating Expense i.e. the cost of
> >operating the value stream - the development organization.
>
> I agree Value is #1, but I don't know how to measure it directly. SIP is
> production lead time, not Takt time (takt in XP is always one week, we
> just vary the size of the unit of production.)
>

I don't think it's true that in XP takt is one week. That's just the time 
frame we use for velocity measurements. Takt is an inverse measurement of 
velocity (instead of widgets per unit time, it states time per widget). XP 
has a concept of velocity, measure in story points per week (iteration). 
The inverse of this is weeks per story point, which isn't very satisfying, 
but isn't one either.

So for a given XP project, I could calculate takt time of, say, one day per 
story point, and see if I was meeting this target or not. If we could 
measure the velocity of story points at different parts of the value chain, 
we could find bottlenecks or wastage, as in the example on the web page. 
It's not clear to me how to do this, or if it's even worth trying.

Steve


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