Time and again I run into scenarios where trying to satisfy all the scheduling practice standard guidelines can leave you in a no-win situation. For the purposes of this article I’ll call these Practice Standard Conundrums – that which seeming cannot be solved without violating at least one scheduling practice standard guideline.
Today I’m going to talk about activities that have no logical successor. These come up from time to time and are always problematic: particularly if they are in the earlier months of a project’s lifecycle.
In our Primavera P6 Professional Fundamentals training class, we use the Wellmont electrical substation sample project. In this project, there is a good example of an activity that doesn’t have a logical successor. The ‘Install Fence’ activity is dependent on the ‘Grade Site’ activity being complete before it can start. However, no other elements of the project are truly dependent on the fence being finished. Therefore it really has no successor except perhaps for the project complete itself. That is to say if the work on the fence was delayed, it wouldn’t really be pushing on any other tasks.
Furthermore this activity will show up in the schedule log as an ‘activities without successors’ warning.
The conundrum here is that practice standards say all activities except the very first and very last activity should have a predecessor and successor. So we need to link this activity to something in order to satisfy that guideline. We could say that the project cannot finish until the fence is complete: as it would be too dangerous to have a live 60kv electrical substation with no fence around it.
If we link it to the project complete milestone we will satisfy the relationships guideline, but it still leaves the activity with what’s known as High Float. For example, the DCMA considers activities with a float greater than 44 days as High Float. In this case our activity has 49 days of float.
And there is our conundrum.
We could use a constraint to reduce the float on the activity. However practice standards generally discourage the arbitrary use of constraints for anything other than contractual or externally enforced dates. So using a milestone would also violate scheduling best practice guidelines.
If we are using P6 as our scheduling system, we can remove float on open-ended activities by selecting the ‘Make open ended activities critical’ setting in the schedule options dialog.
However this doesn’t really play into the spirit of scheduling best practices. Where using a special feature of P6 to hide some float and make the activity artificially critical.
It would be more legitimate to use a finish constraint to lose float on the activity than it would use this setting. But frankly neither approach is good, and as we’ve already said using constraints to hide float would be “gaming the system”.
The best answer to this conundrum is to use some common sense and think more broadly about the completion of the fence in the context of this schedule.
Let’s take a look at some of the activities that are taking place shortly after the completion of this fence. Do any of these look like they might benefit from the fence’s existence?
What about the lay stoning and lay roadway activities? These also have a lot of float but are somewhat separate from all the other activities. However it may be better to have completed the fence line before we start the Lay Stoning activity. So let’s see what happens if we were to create a link from Install Fence to Lay Stoning. And while were about it, let’s remove the link to the project complete milestone.
This actually worked. It reduced the total float on the Install Fence activity to just 32 days, down from 49 days. If we check the schedule log after making this change, we’ll see that we are back to just two activities in the warnings area.
Summary
So we managed to find a way out of the conundrum and keep our schedule in good standing with scheduling practice standard guidelines. This is just one of many conundrums you may find yourself dealing with when trying to raise the quality of your schedules.
While it takes a little more time to think these things through, it’s definitely worth doing. In my role as teacher and consultant, I see many schedules that have been rejected by the company’s customer based upon poor adherence to a scheduling practice standard. It wasn’t because the scheduler didn’t care, or did a bad job, they just didn’t know.
Schedules that had been working very well for their other projects are suddenly being held to a higher standard by industry practice standards. So while some scheduling practice standard guidelines cause conundrums, you’ll still have a better schedule when you take the time to learn about the industry standards.
Good sources for these are the PMI’s Practice Standards for Scheduling, and the GAO Schedule Assessment Guide GAO-16-89G (recommended by this author), to name just two.
Related Articles
Other related articles on the subject of scheduling practice standard guidelines also include, but are not limited to:
GAO Releases Schedule Assessment Guide
A More Descriptive Solution to the Negative Lags Dilemma
Understanding the Primavera P6 – USACE Mandatory Requirements
A Short Walk through the NAVFAC IPS Checklist
Scheduling Best Practice Guidelines For Primavera P6 – Video Training Course
Who Needs Scheduling Best Practice Training?
DCMA 14-Point Assessment and Missed Tasks
The DCMA 14-Point Assessment and Schedule Relationships
The DCMA 14-Point Assessment and Hard Constraints
DCMA 14-Point Assessment – Invalid Dates
The DCMA 14-Point Assessment and The Schedule ‘Lag’ Inspection
The 14-Point Assessment and Schedule ‘Missing Logic’ Inspection
DCMA 14-Point Assessment and High Duration Tasks
DCMA 14-Point Assessment and the Critical Path Length Index
DCMA 14-Point Assessment and the Critical Path Test
How Deltek Acumen 8.0 Will Help Prevent DCMA Surveillance Audits
The DCMA 14-Point Assessment and High Float Tasks