Creating and Managing Constraints

Together with dependencies, constraints determine how multiple tasks within a project must be sequenced and scheduled.

Assigning constraints to tasks is an important part of making sure that multiple tasks within a project are appropriately sequenced and scheduled. Most constraints serve one of two functions: minimize the time between successive tasks, or schedule tasks in such a way that subsequent tasks or the project at large are not delayed overall.

Moreover, constraints help ensure that project teams have completed the necessary predecessor tasks to be able to embark on subsequent tasks when they arrive in the project schedule.

In Spreadsheet.com, constraints are created and managed through two specialized data types: Constraint type and Constraint date.

Spreadsheet.com supports eight different types of constraints to reflect the different relationships between your tasks:

Constraint

Abbreviation

Type

Description

As Soon as Possible

ASAP

Flexible

The task begins at the earliest possible date depending on its predecessor tasks

As Late as Possible

ALAP

Flexible

The task begins as late as possible without delaying dependent tasks

Finish No Earlier Than

FNET

Semi-Flexible

The task must finish on or after a specific date

Start No Earlier Than

SNET

Semi-Flexible

The task must start on or after a specific date

Finish No Later Than

FNLT

Semi-Flexible

The task must finish on or before a specific date

Start No Later Than

SNLT

Semi-Flexible

The task must start on or before a specific date

Must Finish On

MFO

Inflexible

The task must finish on a specific date

Must Start On

MSO

Inflexible

The task must start on a specific date

Learn more about each constraint type in our article Introduction to Constraints.

Assigning Constraints to Tasks

When you create a new dependency in Spreadsheet.com, it will automatically be assigned the As Soon as Possible (ASAP) constraint. If you want to retain the ASAP constraint, no action is required. Or, you can change it to one of the other constraint types supported by Spreadsheet.com.

Before editing constraints, your worksheet must have columns with the Constraint type and Constraint date data types. Constraint date columns can be formatted to include date or date and time values.

constraint-dts.png

Both Constraint type and Constraint date are strict by default and can only be applied at the column level. Constraints can be enabled by manually adding these columns to your worksheet, or by enabling these columns in Project Management settings.

How to Change a Task’s Constraint Type and Date (in sheet)

  1. Click the dropdown arrow in the row’s Constraint Type column
  2. Select a new constraint type from the dropdown list
  3. If necessary, specify a constraint date in the row’s Constraint Date cell

edit-constraint.gif

How to Change a Task’s Constraint Type and Date (on Gantt chart)

  1. From the Gantt chart, click on a taskbar to open the event dialog
  2. Use the dropdown fields to edit the Constraint Type and Constraint Date

open-event-dialog.gif

Alternatively, you can edit a task’s constraint type and date by dragging and dropping its taskbar on your Gantt view. When you drag and drop a successor task, it will take on the Start No Earlier Than (SNET) constraint type with a constraint date of the task’s new start date.

drag-and-drop-constraint.gif

By using this method, you can only establish a SNET constraint for the task being moved.

Visualizing Constraints on the Gantt Chart

On the Gantt chart portion of a Gantt view, most constraints are represented by vertical blue bars adjacent to taskbars. FNET, SNET, FNLT, and SNLT constraints are represented with dotted vertical blue lines on their associated constraint dates.

dotted-constraint-line.png

MFO and MSO constraints are represented with solid vertical blue lines on their associated constraint dates.

solid-constraint-line.png

ASAP and ALAP constraints are not represented visually on the Gantt chart.

Looking for a refresher on the different types of constraints and how they affect project tasks? Take a look back at our Introduction to Constraints article.