As Built Critical Path

Hi Guys,



Hope you all had a pleasant XMas, and all my best wishes for 2005.



What is the point of planning, how to work out the best way to carry out a project, and then to monitor it as the work progresses. Therefore, planning is all about the future, and what is past is history.



The reasons for analysing an as-built schedule may vary from project to project. This depends on the purpose of the analysis, ie whether it is for a claim,improving future planning or even to see why the planning was successful or a disaster, etc.



The point I stiil make is that history is in the past and cannot therefore be critical. The events that happened might have had a serious impact on the future, and even if they were critical at the time, cannot be changed. I think the point of history is analysing the mistakes/positive achievements and using this information to improve the future.



So instead of discussing this so-called enigmatic "AS-built critical path", let’s rather discuss more beneficial ways of using as-built schedules, to improve future planning.



Regards



Philip J

Gerry et al



Being an "As-built critical path ’o-phile" I’ve found the thread interesting.



It seems to me that the answer has to be yes - it exists!

Subject to the information being available a skilled planning analyst can surely advise what was critical at any point in time on the project. If we also believe the critical path can switch, then surely connecting all the retrospectively determined critical activities together results in (yes wait for it ...) the "as-built critical path".



Of course you could all just be talking about the ability to locate the as-built critical path via programming software (i.e. via a logic linked dynamic as-built programme) then I would say it is possible in threory - its just not reliable!



Gerry - get back to work!



Regards

David



If we can say in retrospect what was critical at any point in time (using analysis) then

Jaco,



Your example with the 2 Iso’s.



You do not say if the float on the 2 Iso’s is the float on the original as-planned programme or what was available at the time of issue of the Iso’s.



A claim, for eot or delay, that is based on the float as shown on the as-planned programme only would not succeed.



It it is the float at the time the the Iso’s were issued, then the contractor is entitled to a 5 day eot for late issue of Iso 1. Most contracts encourage an extension of time to be awarded when the completion date is "likely" to be delayed, i.e. at the time of the delaying event.



At the end of the project, to establish actual delay caused by either Iso 1 and/or 2, then further investigation and substatiation is required to support a ’loss & expense’ claim, and not just an as-built programme or as-built critical path.



Sorry, I have digressed from the thread, but this is important. An as-built critical path, or any cpm delay analysis, is there to support or compliment a delay claim; but the delay claim must be based on facts.



Roger Gibson

I am still a Believer in an as Build Critical Path.



Example (Piping)



Two Different Iso.



Iso one

Release Dwg (Activity Critical) (Late 5 Day’s)

Construction Planned 14 Days Actual 7 Days



Iso Two

Release Dwg (Non Critical 10 Days Float) (Late 8 Days NO EOT)

Construction Planned 14 Days Actual 24 Days



Project Delayd 5 Days as per Projected CP (Real Impact none)

Project is Delayed Actualy by 8 Days (Please note non Critical Activity)



The only way how you can see this is after the project is completed. Then you would be able to see that ISO two was the real Critical activity and ISO 1 was not ???.



I know you can argue that the activity become critical but you don’t know the full impact before it is completed.



Cheers

Vladimir,

I was expressing the view that I can understand how the CP can be applied to the future: I was not being categorical or dogmatic about the issue.

I was stating that I am persuaded by the view that a CP can only apply to the future; I was not defining it. Nor have I been persuaded by earlier parts of this thread – within a strict planning and scheduling context – that a CP exists retrospectively.



That is not to say, of course, that I don’t use the term when presenting a delay claim predicated on historical events that have had an impact on the CP at that time.



Cheers,



Stuart



www.rosmartin.com

Dear Stuart,

please advise me where in the definition of the Critical Path I may find that "a "Critical path" can only apply to the future".

Thank you in advance,

Vladimir

PHEW!!! – and I used to get complaints about some of my long threads and wanderings!

I’ve now had a chance to catch up, so let me throw my hat into the ring!!



Having just completed planning an other piss-up in a distillery, I can see this in a different light!

I think that it all depends on which hat you are wearing!



I believe that Martyn and others may be correct in saying that by definition the terms "As built" and "Critical Path" cannot be used together, since an "As built" schedule is one that has been updated with actual starts and finishes, whilst a "Critical path" can only apply to the future. And I am persuaded by this view from a strict planning perspective.



But as Gary also correctly points out, when you are trying to explain the historical events that impacted a Contractor’s performance (in lay terms and often to a lawyer or a sleepy Judge!), the term “As-built Critical Path” is used to describe such causes and effects. The “As-built Critical Path” is a term used (or abused!) to describe the sequence of actual events that happened throughout the execution of the project and which, as a result of their occurrence, had an impact on the Critical Path at that time.



So I think that from a strict or clinical planning perspective, many of you are right in that an “As-built Critical Path” is a contradiction in terms and cannot exist, but from a delay claims perspective, it is a term frequently used to describe the historical events that impacted a critical path in pursuit of a claim for delay.



Does this clarify or confuse? ;-)



Stuart



www.rosmartin.com

Gerry, I have already been given my opinion at the start of thread and no change in the statement so far.

The simple issue has been so pronloged and discussed to understand the word " As built". I think enough and valuable discussion should come into conclusion now.

Jaco,



It is an interesting idea, but you cannot calculate a longest path using actual durations. – Let me put this another way, such a calculation without modifications would be meaningless.



A longest path calculation using just actual durations would ignore that fact that many activities begin before they are logically able to do so. This fact, in part accounts for the increased durations commonly found. In addition to using actual durations, you also need to adjust the logic to account for the actual early starts.



I have been thinking of this issue for a long time. In fact, I have written software called As-Planned/As-Built Maker that creates such a schedule from the As-Built schedule. You can read more on this at http://www.ronwinterconsulting.com/forensic_brochure.htm.



As for relying on what computers ’say’ is correct - first you need to at least know what they are saying. That is why the As-Built Critical Path is so important.

Hi Ronald



Maybe the word Right was not correct BUT the computer program (Example P3) is told to calculate the the Longest Path on Remaining Duration. If you program P3 to Calculate on the Actual Duration it will also give you the "As Build CP"



Have you ever had a case were the schedule tells u this is your CP and you know it is wrong then when you check the logic you find the mistake. We must not rely on Computers and belive everything they "Say" is correct.



As far as Politicians go " I have heard politicians say "I have never had ... with this woman" But then again it depends what you define "...." as. So my conclusion are they always tells the "truth" from their perspective.



Cheers

Jaco,



You need to better define the word, ’right.’ Do you mean ’accurate’ or do you mean ’truth.’ A computer program will not give you truth (neither will a politician.)



A computer program can tell you what the schedule says is the As-Built Critical Path. But then again, isn’t it important to know what the schedule says? Is this not the first step? Without this, everything else is just opinion.



The truth may be something different. I prefer to testify as to what the schedule says is the critical path. This (at least) can be proven.

Gerry



Here is a Thought



The Critical Path can only exist in an As Build State.



The Reason

As so many NON Believers have agreed is that the critical path keeps on changing. So if you say something is Critical now it does not mean it is stil critical in a second/Minute/Hour/Day/Week/month from now.



So to see the true Critical Path you can only see it when you have completed the project. (Not before because it is your "current" projected critical path) (Remember a critical path the longest path)



Cheers

Uri

Remember a computer program is not always right. Just because it tell you does not mean it is right.

Uri,

critical path is by definition the longest path in the network. If I will want to learn what path in my network is or was critical (i.e. longest) I need to look not only in the future but also in the past.

If at the start of the project all activities in my schedule are ALAP then all of them are critical (have zero floats) but still there is a critical path, isn’t it?

Vladimir

Vladimir,



You said the Critical path does not necessarily refers to the future. Just look for a moment at one of your programmes:



Are there any Critical activities to the left of the data date? (in the past)



Is there any float to activities in the past?

Martyn,



I am afraid I cannot agree with you. I have drawn many as-built critical path programmes as part of delay analysis expert witness work. An as-built programme is simple to understand - as you correctly say, it is simply a programme that has been updated retrospectively with actual start and finish dates to demonstrate when each activity actually took place.



To this one can add the actual logic that dictated when each activity took place. By rescheduling the programme, one can demonstrate the as-built critical path. In other words, the longest chain, or chains, of activities through the programme that cause the completion date to be when it was.



This addition of actual logic has to be done very carefully and it certainly demands a considerable amount of close scrutiny to ensure the correct actual logic is used.



In my opinion the use of as-built critical path programmes is not at all uncommon.





Gary France

Chairman

The Planning Engineers Organisation

I really am at pains to understand why this has been such long ongoing thread. By definition the terms "As built" and "Critical Path" cannot be used together. An "As built" scheduled is one that has been updated with actual starts and finishes, a "Critical path" can only apply to the future. An "As built" can only influence the "Critical path" if the actual dates were later than predicted it would then impact the future dependant activities that have not started, possibly creating a "Critical Path".

Gerry,

you described the method of its calculation. I quoted the definition. If some method does not work it does not mean that the problem does not exist.

Vladimir

Critical Path is defined as the longest path in the net. That’s all. Nothing about future or past.

Vladimir

Vladimir,



Explain that one please, about the future?



As I have said before, how can something in the past be critical. Therefore only things in the future have the risk of becoming critical.



Regards



Philip

There is nothing about the future in the critical path definition.

Hi Gerry and all other contributors,



It’s been an interesting one. Thanks all.



An interesting question to PPAdmin what has been the longest thread to date on the site?



Regards



Philip J

Uri,



That’s what I mean, when As-built is combined with the term Critical path it becomes confusing. People tend to interpret it in many ways.



Se

Sigfredo,



I agree with you that there is a problem, however to me the problem is not with the term As-built Programme. This term is commonly used and self explainatory.



The problem lies in the combination of As Built with Critical Path, as usually Critical Path relates to the FUTURE and As Built relates to the PAST.



My personnal opinion is that there is no such beast as ’As Built Critical Path’

"As-Built Critical Path", is it the most appropriate term to use? Can’t we find a suitable term that every time you read it, everyone knows what it means and it doesn’t need clarifications/qualifications when being used. I guess this is one of the reasons why this thread come a long way.



Personally, I find As-built word as confusing as I will immediately compare it with as-built plans. what do you think guys?



Se

Hi Gerry,



How about the question, "Is there merit/purpose in finding this so-called (mystical) AS-BUILT Critical Path?"



Sorry it took me a while to come back, Update Day here:-)



Regards,



Philip J

Gerry

Sorry - I should have made it clear I knew who you were talking to. I just meant to put in my 3-ha’pence-worth!



We are only too weel aware here abpit the EOT issues. Unfortuanately, many of those invloved 9especially rhe lawyers) do not really appreciate thes issues. I think we ought to make a distinction between an as-built schedule (actual dates) that happens to built on a CPM program and a CP schedule (one where the logic is key).

Maybe the only useful question is:



Is there any purpose in looking for an as-built critical path?

Gerry

Just look it is next to the Elbow Grease.

Hi Gerry,



Now you finally found the skyhook, go to the stores and draw a longweight.

Gerry,

we usually create very detailed schedules for construction works with the activity durations that not exceed one week. Contracts define target dates for major milestones and these target dates incorporate agreed contingency reserves.

Vladimir

Happy to know that the wave is seem to be settled on the As Built Critical Path issue ................... Its time for voting as per Philip Jonker’s suggestion.

Hi Guys,



I just had a nice relaxing weekend and have been catching up with all that have been said.



The one subject that seem to have cropped up since my last contribution is a "project without a schedule". Can somebody please define that one for me, I can only understand it as a project for which no planning was done, in which case it does not belong in this forum. Otherwise, I seem to sense that it was not scheduled in the normal way, ie by P3 or MSP etc, ie a computor, but it could have been done in the old fashioned way, as I was taught before the advent of PC’s.

The second point is the notion that a project cannot be completed overnight, in fact a project can be completed in a matter of seconds. What is the definition of a project. There is three areas in every project that is looked at, cost, time and quality, if there is risks involved in any of these areas, and dependant on the amount of risk the undertaking can be rated as project or not. Thus a wedding or a Formula one tyre change can be regarded as a project, and if the pre-planning is disregarded, then what I said about seconds holds true.



Further I agree with Vladimir and Philip, the two previous contributors, as they seem to be saying much the same thing. The as-built CP is a hypothetical notion somebody has thought up, when trying to analise a schedule where the job has been done. Depending on the reason/s for the analysis, whether for a claim, or to establish how future jobs can better planned, there is much simpler ways of getting to the right answers, whether it was a good or a bad schedule. I have stated this earlier, this proves the necessity for proper resourcing of schedules, as well as for good costing practices.



Maybe it is time for a vote:-) Pro as-built CP or anti?



Regards



Philip J

Philip,

let me express my oppinion:



a) The critical path is an assessment of those activities (from now until the end) that could delay the project if themselves delayed. CP in the past is therefore an irrelevance.



It is not quite true, CP does not take into consideration resource limitations. It is true if resource constraints do not exist. CP in the past is useful for the project performance analysis post mortem.



b) By my definition, therefore, there can be no critical path on completion, so no As-built critical path



As Built Critical Path shows which activities and delays defined actual project duration.



c) An hypothetical CP could be constructed from the as-built schedule (which records actual dates, suspend, resume, resources etc). This is useful in informing the next project, in improving the start-up planning



Right, it is useful for lessons learned and for claims assessment.



d) The reconstructed CP is HIGHLY subjective. If the as-built is to be used for a claim, then avoid any links and restrict the plan content to fact, that which can be evidenced.



Right! That is why I wrote that all delays and their reasons should be documented and included in the project model.



e) Above all, remember that the CP is not factual. It relies on a subjective assessment of the relationship between semi-factual activities. Even when activities have been completed, it is still very difficult to ascertain the ’true’ relationship between them.



I don’t agree with the subjective nature of activity relationships.



d) As to whether there is a CP in a project without a schedule - this is largely irrelevant. The CP is one’s idea of the longest path. If one has no ideas (i.e. no schedule) then one can have no concept of a CP. Again, the CP is not an absolute, it is based only on the assumptions made by those involved.



CP is usually based on the technological restrictions (roof after walls, etc.), it is not based on assumptions.



Hope this adds rather that subtracts!

Dear All

If I may make some contribution here and in way of trying to summarise and add to what has gone before:

a) The critical path is an assessment of those activities (from now until the end) that could delay the project if themselves delayed. CP in the past is therefore an irrelevance.



b) By my definition, therefore, there can be no critical path on completion, so no As-built critical path



c) An hypothetical CP could be constructed from the as-built schedule (which records actual dates, suspend, resume, resources etc). This is useful in informing the next project, in improving the start-up planning



d) The reconstructed CP is HIGHLY subjective. If the as-built is to be used for a claim, then avoid any links and restrict the plan content to fact, that which can be evidenced.



e) Above all, remember that the CP is not factual. It relies on a subjective assessment of the relationship between semi-factual activities. Even when activities have been completed, it is still very difficult to ascertain the ’true’ relationship between them.



d) As to whether there is a CP in a project without a schedule - this is largely irrelevant. The CP is one’s idea of the longest path. If one has no ideas (i.e. no schedule) then one can have no concept of a CP. Again, the CP is not an absolute, it is based only on the assumptions made by those involved.



Hope this adds rather that subtracts!

Yes, you are right. Logical restrictions that were established at the project start should be kept. If they were wrong then it is a cause for lessons learned exersize. But you shall add delays and additional work to the original network.

Vladimir,



What does the path that you have identified ’mean’ then?



From your earlier postings, you appear to have maintained the original baseline programme logic links to establish the ’As-Built Critical Path’. Is my understanding of your methodology correct?



Roger Gibson

Sure,

Critical Path may change during project execution and many times. That is why you shall include in As Built Schedule all delays that occured with the description of events that cause these delays. As the result you will see what chain of activities and delays constitutes As Built Critical Path. It does not mean that at any time in the project life this path was critical in the project schedule.

Hi Vladimir,



I think it’s possible but highly improbable to have a logically linked as-built activities at the end of the project.



Experience would tell us that your CP at the start may not be identical a month after, 2 months after etc. and moreso at the end of the project. "Not identical" means, it may have similar activities for each periodic CP but may not be 100% identically the same path.



Se

I mean logically linked as-built activities loaded with resources, costs and other actual information that should be compared with the original estimates.

I repeat that during project execution all schedule delays should be included in the schedule preferably like additional activities (delays) or lags, imposed dates are worse for the future As Built Critical Path analyis.