Constraints

One of our biggest problems with legacy CPM stem from its ability to tackle soft logic.

What is soft-logic?

First, let's define hard logic. This is logic that cannot be altered or changed. For example, you cannot paint a wall, unless the wall is hung and finished. This will always be true, forever until the end of time.

Soft-logic is preference. For example, you might prefer to seal floors first then install the ladder tray, but that's a year from now. When the day comes and you can't seal the floors for 2-weeks for one issue or another, but you can install ladder tray today... Why hold up the job? Or why have ladder tray laying on the floor at risk of damage? Why hold up the other work that the ladder tray releases?

A constraint is a maximum value of a given dimension at any moment in time (a day).

Some examples of constraints:

• 20 workers in a specific area.
• 1 slab pour per day
• 5 column forms per task
• 1 task at a time for a given trade
• 1 task at a time per area

Constraints are blockers

The c-index

The c-index is the number of days you're willing to wait for your preference. In the example above. If you were willing to wait 2-weeks to get the floors sealed before the ladder tray then you would set the "Seal Floors" task's c-index to 10 days. Setting it to 9 days would mean the floors would be sealed today.

There is no maximum c-index value.

Constraints in the schedule calculation

A normal

Constraints and Target Dates