Difference between Retain Logic and Override Progress

Dear Dr. Paul.

Thank you for the contribution. Will keep looking out for the post in the Guild.

Wramest Regards.

Engr. Iyke

it is exactly as it states. Retained logic when an activity have started RETAINIED LOGIC IGNORES THE ACTUAL START DATE AND LOOKS AT THE REMAINING WORK OF THE PREDECESSOR AND WILL NOT PERMIT THE REMAINING WORK OF ITS SUCCESSOR TO BEGIN UNTIL THE PREDECESSOR HAS BEEN COMPLETED. 

If you use progess override it will do just that it will not honor the logic and it si possible that activities will be scheduled to be completed sooner than physcially possibel. i.e. I have an example that show drywall finishing PRIOR to stud which is physcially impossible. Also all float values will be incorrect. 

If you give me your email address I can send you my write up and example.

Iyke,

How Retained Logic, Actual Dates, and Progress Override Deal With Out-Of-Sequence Progress

• Ultimately, it’s our recommendation that instead of relying on the Progress Override and Actual Dates options to deal with activities that progress out of sequence, owners should specify the use of the Retained Logic option and require contractors to address activities that progress out of sequence on an activity-by-activity basis as it occurs and to make appropriate changes to the schedule logic to ensure that the project schedule matches the current construction.

This is so true, a no-brainer broken logic can create all sort of schedule problems; unfortunately some owners might insist in hijacking your schedule and will not let you make changes in logic to your update schedules unless approved after a reluctant review.

• A revised Baseline once approved might represent an implicit change order but not so a schedule update. 
• Schedule updates are essentially informative and shall always represent your true plan; if there is out-of-sequence logic it is a faulty model that might create calculation errors. 
• If the update shows you are far from contract target(s) then the owner might require you to submit a recovery schedule.
• In no way the owner shall prevent you from having your plan.  You are the owner of the means and methods (unless it is a Construction Management Contract) . You have the right to make adjustments to your work plan as need be.
• Why this happens is a mystery to me, perhaps lack of understanding by the owner, perhaps it is because of claims paranoia, but it happens.

Best Regards,

Rafael

Dear Zoltan,

Thanks for your contributions. My email addy is in.wenceslause@gmail.com

Best Regards 

Sent to your email address

f you use progess override it will do just that it will not honor the logic and it si possible that activities will be scheduled to be completed sooner than physcially possibel. i.e. I have an example that show drywall finishing PRIOR to stud which is physcially impossible. Also all float values will be incorrect. 

Anoon,

in resource-constrained schedules the choice of the wrong activity competing for the same resources may lead to large delays. We consider this out of sequence and insist on following the optimal order created by the scheduling tool.

Another case is starting the construction before the drawings were approved. This is risky but usual.

If out of initial sequence was analyzed and approved then it is fine. In other case it may create problems that can be avoided.

Anoon,

I saw. At the start of the shift construction foreman gets the list of the jobs to be done and planned volumes of work. At the end of the shift he enters actual volumes and presses recalculate button. next foremen gets the list of the jobs to be done, etc. Not everywhere, not often, but still this exists.

For "resource constrained schedules": yes, contractor is interested in doing the work faster, but foremen may select one work instead of another that requires the same resources just because he does not see future consequences that are not obvious.

Anoon, you are right. It is something we warn about.

If project schedule was created in the office by some 'planner' who did not get the data and approval from site managers, when the schedule is created and used not for resource management but for management of contracts only, it will not become decision making tool.

As we discussed earlier most "planners" do not resource load their schedules, do not level project resources, do not visit construction sites. Then "out of sequence" may usually mean that the schedule is poor and must be improved.

Anoon,

I expect that we shall discuss the schedules created by real professionals, not amateurs. We both know that most schedules are poor and do not meet basic requirements. But PP is a forum of professional planners that can help to improve approaches and standards of project scheduling. Best practices are rare but still exist.

Resource loading itself requires detailed scheduling. Let's agree that the schedules that can be used for real management and decision making shall be resource loaded and levelled, approved and accepted by site personnel, and only in this case out of sequence may be considered as a problem.

The quality of contractor's schedule is contractor's responsibility.

Out of sequence jobs in contractor's schedule usually tell that the schedule quality is poor and it shall be revised.

But imagine the following case: you have two contractors that shall do their jobs one after another in each room of the building.

The order matters for the second contractor but not for the first. For the first contractor only resource constraints limit the number of rooms done simultaneously.

If the first contractor starts to do the rooms out of approved order it would be necessary to apply retained logic, isn't it?

The following reference might be of interest to this discussion.

• http://ronwinterconsulting.com/Activity_and_Project_Status.pdf
• http://www.ronwinterconsulting.com/Out-of-Sequence_Progress.pdf

Rafael,

common definition of out of sequence does not exist.

In particular the difference of our definition and definition of Ron Winter:

If there is finish constraint (dependency) and it was satisfied then we do not consider that activity execution was out of sequence even if it was started earlier than planned. Managers may use activity flex and assign less amount of resources to do the job without violation of any logical and other restrictions.

Ron considers this case as out of sequence.

The difference in our numbers in Ron's examples was caused by this particular difference in our approaches.

Vladimir,

Got it, very interesting.

I wonder why the abismal difference with P6.

Thank you.

Rafael,

I expect that P6 looks for ongoing activities only ignoring out of sequence events in the past.

here are the differences and why not to use it 

Vladimir,

Same as broken date constraints, broken resource constraints can be interesting, even when not identified as such by the software.

• Perhaps there was no such overload but wrong updating if using wrong workloads but still OOS events.  
• In any case it is good to know OOS [+ OOS type] happened.

Vladimir,

If I got it right this means some OOS events will never be reported by P6 in any update such as when the OOS events happened in between start and finish of the reporting period.

I find Ron_Winter's paper one of the best, and perhaps the best article on OOS ever.  I like his inclusion of broken date constraints as OOS events, irrespectively of what action you decide to take it is valuable to be aware of all broken constraints, knowledge is power.

Because not all OOS events shall be treated equal but in a case by case basis this is another point in favor of the 3 scenarios approach over Monte Carlo.

Best Regards,

Rafael

Yes Rafael, it happens usually when people entered revised actual dates and duration without adjusting resource usage.

Resource reports show periods of resource overloads and entered numbers of resources working simultaneously at any moment. So it is easy to find and to fix wrong data if required.

Vladimir,

Yes Resource Overloads Report gets it right, not so the Overloads Bar.  Maybe the Overloads Bar shall be discontinued in favor of the more reliable report.

Possibly adding Workload field to this report would help to uncover a possible source of updating errors.

I wonder how P6 users would deal with unplanned partial workloads for work done as well as remaining.

Best Regards,

Rafael

If tighter logic (not FS but SS+Lag and FF+Lag) is acceptable then it should be used from the very beginning.

Activity dependencies shall reflect real life constraints and not the way we plan to do the work.

So Zoltan's example shows the case where out of sequence showed that the schedule shall be improved and out of sequence was caused by poor modelling of the real life constraints.

Anoon,

Unfortunately the Chinese as well as the Japanese are missing in PP and literature is hard to find.

Best Regards,

Rafael

Dr. Paul,

in your answer to Rafael you discussed Spider Project and the reasons why it is not widely used.

For your information: Spider Project is used by most construction companies in Russia, in most large scale programs (like preparation of 2014 Winter Olympic Games) and was recognized as the best analytical tool for construction industry by Russsian Government Analytical Center. It is also used in all other industries (aerospace, railways, mining, shipbuilding, etc.).

It has customers in 35 other countries but they are few for many reasons:

1) At the conferences where I participated many people told me that they are impressed by Spider Project but their contracts require to use P6 and they do not have an opportunity to select the tool to be used. One person told me that his management explained him that since their company is involved in Government contracts they shall use only American software. So there are certain barriers that do not permit to select the software for construction management.

2) In Russia construction managers frequently asked me the same question:

Why managers in the West use tools that do not plan and manage volumes of work to be done, do not consider resource production rates, are not able to create and apply corporate norms, do not model project budget, use only one WBS, etc.

What shall I answer? The main reason was mentioned in your post: "I only use the CPM schedule as a guide and nothing more."

It does not matter what tool to use for creating CPM schedule that is not resource and cost loaded and used as a guide.

And you are right - most planners do not create project models that can be used for real management amd decision making, they create guides that may be used for contract management and for nothing else. The culture of planning is poor and declines if to compare with planning in early 90-s.

3) We never advertised Spider Project. The quality of the sofware is so high that it very soon became most popular in Russia by the word of mouth. It looks like this model (happy customers tell others) does not work abroad. It looks like software to be used is selected not by those who will actually work with selected tool.

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And about multiple WBS - as you know Spider Project permits to use multiple WBS since its launch in 1993. The number of different structures is not limited. This feature is always used by Spider customers for more that 25 years.

As for videos: nothing can replace proper planning. By proper planning I mean creating project model that takes into account all existing constraints, risks and uncertainties and finding the best possible schedule and required contingency reserves.

Best Regards,

VL

I wonder why most of the scheduling specifications prohibit the use of progress over ride ?. I guess they are all wrong and Anoon is correct go ahead and use it what could it hurt ? Then you can say HOUSTON WE GOT A PROBLEM! after you use progress over ride.

Anoon thank you for your response and I agree that there will ALWAYS be out of sequence progress that should be corrected.  

Anoon thank you for your response and I agree that there will ALWAYS be out of sequence progress that should be corrected.  

Hi Dr. Paul,

Thank you for your reply.

It looks like we are discussing the same points but keeping in mind different ways of creating and managing project schedule. In our practice schedulers that sit somewhere outside is nonsense. The scheduling is the team work that involves not only scheduler but everybody who is responsible for something (including superintendents). It shall be accepted by everyone and people responsible for different parts of the schedule update them regularly.

An example of work organization on construction site in one Contractor company:

At the beginning of the shift superintendent of the 1^st shift enters the numbers of resources (people and machines) that are available (if different than planned), levels the schedule and gets volumes of work that shall be done in his shift.

At the end of the shift he enters the volumes that were actually done and recalculates project schedule creating its next version.

Superintendent of the next shift does the same, etc.

Changing the work order (out of sequence) requires an approval from PM. If done on site without the permission the special report shall be sent to PM with the explanation why it was necessary.

If nothing wrong happened the schedule is analyzed for potential improvements and corrections weekly.

I described the real case that unfortunately is not common. It is also usual that the scheduler sits in the office and collects data from project participants and updates the schedule daily. If no objections or change requests were received the schedule is considered as accepted.

Owners usually update project schedules weekly.

You wrote about YOUR schedule that is not the same as the schedule created somewhere 100 km away. So you use different schedule but it is still project schedule, isn’t it? Then why do you need that original schedule that is useless?

It is common for contractors to manage three schedules in parallel: Contract schedule (do you mean this schedule as created by somebody that is far away?), Project Management Team schedule (that includes necessary contingency reserves) and Work schedule (that is optimistic). Superintendents gets and works with the Work schedule, the scheduler updates all of them.

As for VR and AR you wrote: Imagine the CPM schedule as not being a 2-dimensional piece of paper but a 3-dimensional video showing the workers exactly what work they are supposed to be doing as well as how the work is going to be done? 

Yes, it is nice to show your schedule using VR and AR but first of all it shall be created and optimized. And this is mathematics that cannot be replaced by AR and VR.

Best Regards,

Vladimir

Hi Anoon,

I described what I have seen in the projects where I participated and which I attended as project management consultant.

You may consider this as an ideal way but it is not unusual in Russia. I found that abroad projects are managed different way - in particular it was strange to me that project scheduler creates project schedule himself without involvement of all project participants that is rare in Russia but common case in other countries. I have made many discoveries that did not anticipate. For example, few contractors abroad level project resources and plan and manage project expenses. Most of our customers work in Russia and their needs, their way of work, their problems are different.

If you think that this is an ideal way why not to follow it?

Anoon,

I believe you and this is sad. I have the same impression talking with the participants of different conferences. There are exceptions but few.

True scheduling works when company owners and top managers understand the value of good planning and what they can loose with poor planning and project control. When they see what money is saved by proper management project planners (we do not have separate term for schedulers) get full support and become powerful figures in project hierarchy. But in any case they are team members and scheduling is the team job. And good planning is easier to implement in small and medium companies where the owners and top managers try to save money. It is hard to implement changes in large companies where people are interested in their jobs but not so much in the results and need to follow methodology created by someone somewhere.