Task Constraints

There are two switches that govern task constraints in OpenAir: “Enable FNLT (finish no later than) dates for tasks” and “Switch FNLT dates to end dates.”

According to Microsoft Project documentation, there are eight Microsoft Project task constraints. They are described in the table that follows.

Type	Name	Description
Flexible	As Late As Possible (ALAP)	Schedules task as late as possible with the task ending before the project ends and without delaying subsequent tasks. This is the default constraint for tasks when you schedule from the project finish date. Do not enter a task start or finish date with this constraint.
Flexible	As Soon As Possible (ASAP)	Schedules task to begin as early as possible. This is the default constraint for tasks when you schedule from the project start date. Do not enter a start or finish date with this constraint.
Semi-Flexible	Start No Earlier Than (SNET)	Schedules task to start on or after a specified date. Use to ensure that a task does not start before a specified date.
Semi-Flexible	Finish No Earlier Than (FNET)	Schedules task to finish on or after a specified date. Use to ensure that a task does not finish before a certain date.
Semi-Flexible	Start No Later Than (SNLT)	Schedules task to start on or before a specified date. Use to ensure that a task does not start after a specified date.
Semi-Flexible	Finish No Later Than (FNLT)	Schedules task to finish on or before a specified date. Use to ensure that a task does not finish after a certain date.
Inflexible	Must Finish On (MFO)	Schedules task to finish on a specified date. Sets the early, scheduled, and late finish dates to the date that you type, and anchors the task in the schedule.
Inflexible	Must Start On (MSO)	Schedules task to start on a specified date. Sets the early, scheduled, and late start dates to the date that you type, and anchors the task in the schedule.

Type

Name

Description

Flexible

As Late As Possible

(ALAP)

Schedules task as late as possible with the task ending before the project ends and without delaying subsequent tasks. This is the default constraint for tasks when you schedule from the project finish date. Do not enter a task start or finish date with this constraint.

Flexible

As Soon As Possible

(ASAP)

Schedules task to begin as early as possible. This is the default constraint for tasks when you schedule from the project start date. Do not enter a start or finish date with this constraint.

Semi-Flexible

Start No Earlier Than (SNET)

Schedules task to start on or after a specified date. Use to ensure that a task does not start before a specified date.

Semi-Flexible

Finish No Earlier Than (FNET)

Schedules task to finish on or after a specified date. Use to ensure that a task does not finish before a certain date.

Semi-Flexible

Start No Later Than

(SNLT)

Schedules task to start on or before a specified date. Use to ensure that a task does not start after a specified date.

Semi-Flexible

Finish No Later Than (FNLT)

Schedules task to finish on or before a specified date. Use to ensure that a task does not finish after a certain date.

Inflexible

Must Finish On (MFO)

Schedules task to finish on a specified date. Sets the early, scheduled, and late finish dates to the date that you type, and anchors the task in the schedule.

Inflexible

Must Start On (MSO)

Schedules task to start on a specified date. Sets the early, scheduled, and late start dates to the date that you type, and anchors the task in the schedule.

If you manually enter a start date or a finish date for a task, Microsoft Project changes the constraint type for that task to Start No Earlier Than (SNET) or Finish No Earlier Than (FNET). These semi-flexible constraint types force the task to start or end on the specified date, regardless of subsequent changes that would otherwise affect the task's place in the overall project plan.