How to build a critical chain!

This is not a summary of an article per se; but it summarizes the description on how to build a Critical Chain as it was published in
Rand, Graham K.: Critical chain – the theory of constraints applied to project management; in: International Journal of Project Management, Vol. 18 (2000), No. 3, p. 173-177.

Critical Chain

The Theory of Constraints was outlined by Eliyahu M. Goldratt in his book „Theory of Constraints“, which subsequently Goldratt applied to project management in „Critical Chain“, which interestingly is a novel similar to Tom DeMarco’s Deadline.  Anyway, the basic idea of the Theory of Constraints is according to Wikipedia

[…] every organization has – at any given point in time – at least one constraint which limits the system’s performance relative to its goal. These constraints can be broadly classified as either an internal constraint or a market constraint. In order to manage the performance of the system, the constraint must be identified and managed correctly […] (from Wikipedia)

The Theory of Constraints outlines a 5 step process to tackle the whole problem

  1. Identify the constraint
  2. Decide how to exploit the constraint
  3. Subordinate everything else to above decision
  4. Elevate the constraint
  5. If constraint has been broken, go back to (1) and never allow inertia to cause a system’s constraint

So what is the constraint on a project? Of course it is the time of critical resources. What is the problem with them? They do suffer from something called student’s syndrome – no matter how much buffer they get, the work is only done in the last few days.
The solution? Exploit the constraint – then elevate it. In other words: finish task on time before trying to decrease total time.
How can one exploit the constraint? Remove all buffers into a big one at the end of the project. All tasks or streams which are not on the critical path get a feeding buffer right before they feed into the critical path again.
How do I manage it? Project Management needs to ensure that no time is lost on hand-overs. Furthermore if the time comes everything must be dropped and everyone works on tasks on the critical chain only. Never ever shall multi-tasking occur!

Leave a Reply

You must be logged in to post a comment.