CORRECTION: Note the following text is an updated correction in this article:

Task calendars can be used to good effect if, for example, a specialist person or a piece of equipment is only available on certain dates and times. It is also useful when you need to force Project to schedule a task to start on a specific day of the week, say Fridays. Create a one minute task and assign it to a task calendar that only allows work on Fridays 0800 to 0801. Insert it between two Finish-to-Start tasks, making it a predecessor of the task that must start on a Friday. Then, no matter which day the predecessor finishes, the one minute task can only be scheduled on a Friday whence its successor can begin. Subsequent tasks will then be one minute out; so, if this is important, subtract one minute from its immediate successor.

Last month I said that we have now covered the very basics of getting a project up and running. So in this New Year, we’ll have a look at more detailed facilities that Project provides to help us to examine and fine tune our projects. This month we’ll begin by looking into more detailed ways of manipulating tasks to meet specific requirements.

Constraints

Setting Constraints

Activate the Task Information form and select the Advanced tab.

In the Constraint type: box, select the constraint necessary that gives the most flexibility, then enter the date to its right. As Soon As Possible is the default setting, meaning that there are no constraints when scheduling from the project start (other than those of the logic dictated by the task dependencies already set). All constraints set can be viewed by applying the Constraint Dates table (View/Table:Entry/More Tables…/Constraint Dates/Apply).

Constraints should be used sparingly as they reduce the flexibility that Project has when levelling. Resist the temptation just to change the start date—leave this to Project’s calculation.

Constraints can also be set inadvertently by moving a Gantt chart bar to change its start date. Project will show a constraint indicator in the Indicator column. Hovering the cursor over the constraint indicator will reveal a tool tip stating the constraint set: be sure this is what you desired.

Definition of Constraints

The following table lists and describes the constraints available in Project:

Hard and Soft Constraints

By electing for soft constraints in the Tools > Options... > Schedule tab (switch off tasks will always honor their constraint dates), tasks depending upon predecessors will still be scheduled to reflect reality, but flagged with a negative slack alert. Soft constraints can move, but only in relation to their links with other tasks, rather than be scheduled firmly according to their constraint dates.

Deadlines

From Project 2000, tasks can include a Deadline date that allows an indicator to be displayed in the Indicator column if a task’s Finish date is later than the Deadline. Enter the date in the Task Information dialog, Advanced tab and view the arrow on the Gantt chart.

No indicator displays if a task finishes before the Deadline. This provides a visible yet unobtrusive notification that the current scheduled Finish is later than the planned Deadline.

[Note that if the Gantt Chart Wizard is used, the codes for the Deadline are deleted (Corrected in 2002 onwards). These can be reset in the Format > Bar Styles dialog – see Bar Styles.]

Splitting

Another way to resolve overallocations is to split the task. From the standard tool bar select the Split Task tool button or Edit > Split Task.

Move the mouse cursor to the start date of the part of the Gantt bar to be split, click and drag to the right. The text box will reflect the start and finish date of the split remainder. Let go of the mouse when finished. Gantt bars can be split as many times as you wish by repeating the process on a split bar.

Edit or correct by re-selecting the split part and dragging as required. (You can more accurately create the same effect by entering zeros in the Work field of the Task Usage view - more of that later.)

Task Calendars

Project 2000 introduced Task Calendars. These allow you to get Project to ignore the Project(Standard) calendar and any calendars for any resources assigned, allowing you to create schedules specific to that task. Task calendars are created through Tools/Change Working Time…/New.

Assign a Task Calendar through the Task Information dialog, Advanced tab. You can also select whether or not to ignore resource calendars.

Task calendars can be used to good effect if, for example, a specialist person or a piece of equipment is only available on certain dates and times. It is also useful when you need to force Project to schedule a task to start on a specific day of the week, say Fridays. Create a milestone and assign it to a task calendar that only allows work on Fridays. Insert it between two Finish-to-Start tasks, making it a predecessor of the task that must start on a Friday. Then, no matter which day the predecessor finishes, the milestone can only be scheduled on a Friday whence its successor can begin.  

Next Month

Next month we’ll have a look at the thorny subject of assigning multiple resources.

A Happy New Year to all my readers and may all your projects be fruitful!