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Regarding Lag value

12 replies [Last post]
Sun, 2009-09-06 00:14
Shah. HB
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Hi to all

Is there any scheduling rule for mentioning lag to successor
I came across a civil construction pro gramme where i found for some activities he has mentioned lag of 52 days.
Please respond
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Replies

Thu, 2009-09-10 16:18
#1
Shah. HB
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Alright Thanks Mr.rafeal
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Thu, 2009-09-10 08:28
#2
Rafael Davila
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Mike

In the metaphorical, absolutely. Your response is welcomed as to uplift our spirit, thanks.

Shahul

“out of sequence will not accepted by consultant” in theory this is how it should be. In my practice it does not happens this way even when the assumptions by the software solve the issue in the majority of cases this is not necessarily always true. At home Consultants do not notice, the reality usually is that the Owner does not have a reviewer knowledgeable of CPM. This is no heaven where everything is good.

None of the assumptions, schedule override or retained logic nor any other can be said to effectively and without exceptions can solve the issue it is just a setting to allow the software to continue with the computations and warn you of the occurrence. Any settling that hides the occurrence is no good.

Best regards,
Rafael
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Thu, 2009-09-10 07:49
#3
Mike Testro
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Hi Rafael

I agree - there should be absolutely NO EXCEPTION to the No Absolutes rule.

Best regards

Mike Testro

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Thu, 2009-09-10 07:31
#4
Rafael Davila
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Recently a wise PP member told me “there are no absolutes ….”, I believe him so correct I adopted his words as if mine.

THERE ARE NO ABSOULUTES

Newton was wrong.
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Thu, 2009-09-10 04:13
#5
Mike Testro
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Hi Rafael

I can’t Of course let you get away with this:

"the Forensic Analyst and those who want to capture Action Schedule into a pure delay analysis tool do not like to accept there is and will always be some arbrtrarity in logic and durations."

Adjusting the logic to suit changed circumsatances is precisely what a skilled delay analyst has to do when adjusting impacted planned to reflect the As Built picture.

It is an integral part of the Dark Art.

Best regards

Mike Testro-
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Thu, 2009-09-10 00:19
#6
Shah. HB
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Thanks Mr.Rafael

But programme with out of sequence will not accepted by consultant, am i correct?
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Sun, 2009-09-06 10:47
#7
Rafael Davila
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Mike

FS links won’t necessarily prevent out-of-sequence.

That out-of-sequence occurred should be highlighted, even when it just means a change in course, it should be transparent anyway, an adjustment like some adjustments we make on a daily basis, and so what? Of course the Forensic Analyst and those who want to capture Action Schedule into a pure delay analysis tool do not like to accept there is and will always be some arbrtrarity in logic and durations.

I believe Powerproject trick solves the issue by splitting the out-of-sequence activity and eliminating all or some predecessors from the first, in scheduling this can be called a dirty trick, if this is the case you must be warned about where this procedure was applied and manually solve the predecessors for the first split. As a demo user I tried this functionality but the activity had only one predecessor, so it ended up with no predecessors when maybe just a reduction in lag would do it. The problem with Asta approach is that it does the trick without warning when and where while P3 keeps the warning about out-of-sequence until you fix the logic.

After the out-of-sequence occurs and it is reported, then and only then you might use the software to do the trick if it is in order as I suspect it will in the majority of cases. In this way you avoid out-of-sequence flags in further reports the same way if you solve other out-of-sequence events as soon as they occurred.

I want to mention that even as a demo user Asta response to my questions was fast, in my experience as no other.

Break the rule, "Out of Sequence" is good! Not knowing it happened is the issue.

Best regards,
Rafael
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Sun, 2009-09-06 09:33
#8
Mike Testro
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Hi Rafael

The problem disapears when only FS links are used.

If a task is completed out of sequence then PowerProject will link around it and retain the logic.

Why create a plan that is flawed from the start.

In the real world you can’t paint a wall until it is plastered - why pretend that you can?

Best regards

Mike Testro
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Sun, 2009-09-06 09:22
#9
Rafael Davila
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Neither do I.

We have to live with out of sequence as real life planning is not perfect, something hard to swallow for the Forensic Analyst.

Planning and scheduling is not perfect and sometimes you got no other option than to make arbitrary planning. Of course better some planning than none under the excuse it is not perfect. It is common to plan for an arbitrary lag and then you make the arbitrary decision to change it.

By the way I encourage my contractors to break the rule whenever changed conditions render it the way to go.

Break the rule, "Out of Sequence" is good!

Best regards,
Rafael
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Sun, 2009-09-06 09:12
#10
Mike Testro
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Hi Rafael

I have not yet received an answer to how to retain the logic when progress on a bar overtakes the mid chart lead lag point.

If anyone can tell me how this problem is overcome I may be a bit more relaxed about mid chart lead lags.

Best regards

Mike Testro
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Sun, 2009-09-06 08:45
#11
Rafael Davila
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I believe Lag as many other advanced functionalities are needed to model complex real word situations even when most of the time lag value is somewhat arbitrary. Somewhat arbitrary because at times there is no absolute, it represents a choice by the planner, an arbitrary choice as well as many real life choices.

The so called way around methods are as arbitrary and are merely tricks to mimic the arbitrary lag using or splitting activities with arbitrary durations.

Lags tend to hide logic but I believe it is because many of the software available do not provide you to with a way to filter for it. A few have adopted the attitude to avoid advanced functionalities as this makes them hard to follow logic while others have adopted the attitude to provide the required functionality to follow logic. One of these is the methodology to determine Longest Path as per Ron Winter that provides you with a practical software application.

Good modern practice calls to use lag with moderation and do not prohibit its use.

PDM does not invalidate traditional CPM it just adds much needed functionality. It is up to you to keep in the 60’s or move to the 70’s and after.

By the way, modern recommended practice for construction jobs with a schedule scale of 20 days for constrution activities do warn about lag of more than 10 days and recommends it to be analyzed on a case by case.

Sorry real life is not that easy.

Best regards,
Rafael
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Sun, 2009-09-06 06:12
#12
Mike Testro
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Hi Shahul

Lead lags should be avoided completely EXCEPT for curing or drying out periods and then they must be set up carefully so that the lag represents calendar days not work days. (not all software has this facility as the outgoing link takes on the caledar attached to the successor task)

If there is any other reason why one task has to wait 52 days after another has finished then a task should be in place with the correct name so the reason for it is clear.

Best regards

Mike Testro
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