We're working on a project that has a considerable amount of task insertion risk (by which I mean either a) the insertion of new tasks into the WBS or b) the rearrangement of technical dependencies in the project network). Despite our best efforts on the WBS phase, we still find ourselves constantly revising the WBS/project network as we learn more about the domain.

My experience is with scheduling tools (e.g. PERT, Monte Carlo) that focus on task duration risk. I'm finding myself very poorly equipped to deal with constant changes to the WBS/project network themselves.

Are there more appropriate tools for me to use for scheduling/control in the presence of high task insertion risk? If so, what are they? I've taken a look at Critical Chain / Buffer Management but am not sure if this is the answer.

  • It sounds like you are spending as much time learning as creating. Are you using any sort of agile/iterative approach now? Sep 11, 2015 at 21:29
  • Dumb question, but isnt Agile for software development?
    – MikeRand
    Sep 12, 2015 at 4:41
  • 1
    No, not just software development: en.wikipedia.org/wiki/Agile_management Sep 12, 2015 at 4:51
  • Why is the WBS changing so frequently with such impact? Surely the scope cannot be changing so much as if that were the case you should not be initiating a project until scope settles down...
    – Marv Mills
    Sep 12, 2015 at 9:22
  • I wouldn't say scope is changing, I'd say that we're all learning as we go how to build this operating facility from scratch. The end state is pretty clear; we need to be able to produce widgets within 9 months. The how (whether expressed as changes to RBS or WBS) is what we're learning.
    – MikeRand
    Sep 12, 2015 at 10:09

1 Answer 1


This is why I prefer a product oriented WBS. Except when the deliverable is a service, the WBS should be based on the product itself, broken down to its components, and then underneath add activities and tasks. Where you load resources is up to you but I typically load them at the lowest level product WBS. Below this, I could not care less what changes are made below because it does not affect the cost or schedule baseline.

Whether you add or take away tasks, it doesn't matter with this set up. If you planned on four coats of paint but ended needing eight, add them. Your "painted wall" does not change so the WBS does not change. This does not constitute a re-baseline but will likely cause a variance. PM is about managing variances.

If you take things out of sequence than your original plan, than simply add actuals to your schedule to show what has happened. Example, if a task had a FS relationship with its predecessor, but the relationship was soft, i.e., it could start earlier, and you did start earlier, simply plug in the early date and break the dependency. Do not re-baseline but let the schedule produce the variances it will produce against the baseline.

It sounds like you are chasing perfect. A perfect schedule means either 1) you are extremely extremely lucky, like 1,000,000,000:1 lucky, or 2) you're cooking the books. And two is most likely.

If there is a huge change that does really constitute a re-baseline, then handle this through your change control process. Re-do the schedule and punch a new baseline and proceed.

  • +1 Totally agree, it's all about the granularity of the information you are trying to model in the WBS and I think the OP is aiming at a level that is too low. IMO part of the art of project management is knowing where to draw that line for maximum effectiveness and minimum schedule and cost risk.
    – Marv Mills
    Sep 14, 2015 at 10:35
  • I think this resonates with me. Our WBS is definitely task oriented, and my argument all along has been "I'm not sure what tasks I need to go through to get this set up, I just know that it needs to be set up". Which I think sounds much more like a product/deliverable oriented WBS.
    – MikeRand
    Sep 14, 2015 at 12:41

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