Guild of Project Controls: Compendium | Roles | Assessment | Certifications | Membership

Tips on using this forum..

(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?

(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.

Mandatory Constraints

2 replies [Last post]
Mon, 2003-06-16 07:46
Srinivasan Ramasamy
User offline. Last seen 17 years 39 weeks ago. Offline
Joined: 14 Jun 2003
Posts: 6
Groups: Petro-Chem / Oil & Gas
How about the usage of mandatory constraints in a schedule. normally i use the mandatory constraints for a certain milestones and project finish dates. But, recently, had a dispute with my client regarding this. It is said that the mandatory constraint will reflect a wrong logic when the activities get delayed. instead they want me to use early / late constraints. but in case of early / late constraints the schedule will never be critical pushing the finsih date as the project gets delayed keeping the lag intact. but still i would like to get some ideas of you, experts about the usage of mandatory constraints.
Top

Replies

Tue, 2003-07-08 22:39
#1
Jorge Taguinod
User offline. Last seen 2 years 18 weeks ago. Offline
Joined: 8 Jul 2003
Posts: 139
Groups: P6-IAP Jedis, Petro-Chem / Oil & Gas, Pinoy Planning Planet Community
Whew! Well said, Paul!

Jorge
Top
Tue, 2003-06-17 06:09
#2
Paul Harris
User offline. Last seen 1 year 3 weeks ago. Offline
Joined: 11 Apr 2001
Posts: 618
Groups: Content Moderators, GPCCAR Editors
I am not a great supporter of “Scheduling Rules”, but I do feel it is important to understand how constraints work and then it is possible to explain to clients why the constraints are selected and what effect they have on the schedule.

During the forward and backward pass the Early and Late dates are calculated and in P3, it is important to understand this process to understand how constraint operate:

Early Start and Finish constraints operate on the Early date calculations.

Late Start and Finish constraints operate on the Late date calculations.

Start and Expected finish date constraints operate on both Early and Late dates and are effectively applying Early and Late constraint at the same time but still allow float calculation to pass through them.

A mandatory constraint operates differently to other constraints. Mandatory constraints do not allow float calculations to pass through them. A mandatory constraint in the middle of a schedule will effectively break the schedule in too two separate forward and backward pass calculations.

Zero Free float makes the activity As Late as Possible by absorbing all the Free Float, in MSP an As Late as Possible constraint absorbs all the Total Float and delays all the successor activities, P3 only delays the task with the constraint.

Zero Total Float sets the late dates to equal the early dates so an activity with this constraint will not display any float.

The final constraint that may be applied to a schedule is a Project Must Finish by date which imposes a Late Finish on all project tasks and float is calculated to this date when set, otherwise float is calculated to the last activity in the Critical Path.

I suggest that you play with a small schedule and get to understand how the constraints work and then apply the most suitable constraint to the environment and explain with authority why a particular constraint has been used.

Regards
Paul E Harris
www.eh.com.au
Top