Gantt LWC - Adding Constraints to Your Project Schedule

Constraints are the scheduling limitations that a project task must operate within.

The project task start or finish date defaults to the project start date (for forward-scheduled projects) or project end date setting (for backward-scheduled projects). Project tasks with predecessors are rescheduled as-soon-as-possible (ASAP) following its predecessors (for forward-scheduled projects) or as-late-as-possible (for backward-scheduled projects). When the project start/end date setting is adjusted, or when the predecessor task is rescheduled, the scheduling engine automatically adjusts the project task start/finish dates.

There may be instances wherein a project task needs to start or finish by a particular date. For example, imagine that you have a task scheduled for a technician to go onsite to do an installation on a specific date. However, for the installation to happen, you need to make sure that the predecessor task - let's say the predecessor task is for the hardware delivery - is completed by a specific date. In this instance, you might set a "Finish no later than" or "Must finish on" constraint for the predecessor task to ensure that it is completed before the installation. Adding a constraint to a task prevents it from being rescheduled when the project start/end date setting is adjusted, or when its predecessors are rescheduled.

Adding Constraint Type & Constraint Date Columns to the Project Schedule

By default, the Constraint and Constraint Date columns are hidden in the project schedule. To add them, simply right-click on any column heading, go to Columns and select both Constraint Type and Constraint Date.

Constraint Types

There are six (6) constraint types available for you to choose from. They are as follows:

Hard Constraints

A hard constraint means that the task has to start or finish on a particular date (constraint date) and cannot be rescheduled.

• Must Start On - the task must start on a specific date (constraint date).
• Must Finish On - the task must finish on a specific date (constraint date).

Flexible Constraints

A flexible constraint means that a task can be rescheduled as long as it does not violate the constraint date.

• Start no earlier than - the task cannot start earlier than the constraint date.
• Start no later than - the task cannot start later than the constraint date.
• Finish no earlier than - the task cannot finish earlier than the constraint date.
• Finish no later than - the task cannot finish later than the constraint date.

When you add a constraint to a task, it will not be automatically rescheduled if the project's start or end date changes, or if its predecessor tasks are rescheduled.

When you remove a constraint, the task is rescheduled as follows:

• Forward-scheduled projects
  • Task has no predecessor - Task Start Date is rescheduled to the same date as project start date
  • Task has a predecessor - Task start/finish date is rescheduled as-soon-as-possible following its predecessor.
     
• Backward-scheduled projects
  • Task has no predecessor - Task Finish Date is rescheduled to the same date as project end date
  • Task has a predecessor - Task start/finish date is rescheduled as-late-as-possible following its predecessor.

Constraint Violation Messages

As previously mentioned, when you add a constraint to a task, it will not be automatically rescheduled if the project's start or end date changes, or if its predecessor tasks are rescheduled. Instead, if the project start or end date changes, or if its predecessors are rescheduled wherein it's causing the task with a constraint to violate its constraint, you are prompted with a constraint violation message.

• Deactivate dependency - this means that a previously defined relationship between tasks is no longer in effect. When you select this option, it will keep the dependency line connecting the task with its predecessor in the Gantt chart. However, the dependency line will display as a broken line to indicate that the previously defined relationship is no longer active. Any changes made to the predecessor task will no longer impact/reschedule the successor task.
  
  Example of a deactivated dependency between tasks in the Gantt chart:
  
  
   
• Remove dependency - when you select this option, Inspire Planner eliminates/removes a previously established link between the task and its predecessor.
   
• Remove constraint - when you select this option, Inspire Planner removes the task's constraint and the task is rescheduled according to the project start or end date (if it has no predecessor), or according to its predecessor task.
   
• Cancel the change - will cancel the change you made to the schedule that is causing the task to violate its constraint.