In Microsoft Project constraints can be used to create a link between a task and a particular date. By default all tasks are created with the Constraint type ‘As Soon As Possible’ set. This allows MS Project to schedule the task on the basis of its duration and dependencies, rather than against a particular date.
Sometimes you need to prevent MS Project from rescheduling a task away from a key date. For example, imagine you are managing the delivery of a conference. The date of the conference is likely to have been booked for months and is probably immovable. In this instance you might set a ‘Must start on’ project constraint for the date of the conference.
Assuming ‘Conference day’ has other tasks linked to it (it should), Project will warn you that a constraint might cause a future scheduling conflict.
That is fine because if one of the tasks linked to the Conference day takes longer than planned then we need to know if it will conflict with the Conference start date. Let say that Arranging the AV equipment was planned to take 2 days, but we find that actually it will take 6 days. If we increase the duration to 6 days MS Project will warn us that there is a scheduling conflict (see below).
So Project Constraints can be useful and have a valid part to play in project planning. However, they can also be created by mistake with dangerous knock on effects. In part 2 see how accidently setting constraints can impact your project plan.