Focus on Workflow instead of plans

Recently I watch the Mary Poppendieck's video "The tyranny of the plan", which is another good video about agile. The key point of the presentation is - Focus on the workflow instead of the detailed plans
I put some of the notes here:

3 main principles:

1.  Design the system to meet the constraints; do not derive constraints from the design.
2.  Decouple workflows; break dependencies!
3. Workflows are easier to control & more predictable than a schedules.

Mary used the Empire building example is used to support the principles:
   Start with the constraints, then design the system to meet the constraints;
   design based on the schedule (constraints);
   schedule does not depend on the detailed design.

What I learned is that the system design depends on constraints, which might be resource, schedule and cost, etc. while schedule should not depend on design. This is a 180 degree reverse of the mindset change.
  
The problems of the schedules.
We need schedules because:
 -  To control when things happen, but
     Detailed schedules are deterministic and do not allow for normal variation.
     Managing a level workflow is a lot easier than following a deterministic schedule.
 -  To predict when things will happen, but
    Schedules based on experience are reliable; if it is based on wishful thinking are not
    When reality does not match the schedule -  the schedule hypothesis was dis-proven!
 
 The workflow is more flexible, always updated based on the situation, "plan is bad, planning is good"

Pull scheduling
 Mary also mentioned the pull scheduling, pull scheduling is time-boxed:
 don't scope box,  don't ask how long will this take, ask what can we done by this date?
 I think which is the concept from Lean/Kanban. I will check it in detail later.

 Resources:
 1. Presentation video
 2. PPT, which is different from the presentation, but actual concepts are same.