As Built Critical Path

You had logic in the initial schedule. What happens with this logic? You had done the work out of sequence? It means that the logic was wrong in your initial schedule or you decided to use fast tracking. The latter decision should be accepted at some moment and the links in the schedule updated.

I still don’t understand what can happen with the project logic to the end of the project.

As Built Critical Path may be useful for project close out, lessons learned, etc.

I don’t understand many arguments in this discussion. Why everybody agrees that there is not such thing as As Built Schedule? Maybe you mix methodology and tools? Just imagine that you do everything manually. In this case you may update your initial schedule with the actual durations and costs and as the result you will receive as built schedule. This schedule has the same properties as any other, including critical path (only if you add into schedule events causing delays).

Gerry



Why would you like to show the as Built Critical Path. - For Future information so next time you start a similar project you can learn out of past experience. Also when you do OME lvl schedules you have a look at your past schedule and this will give you an indication as to the overall duration. (If you have similar constraint) Also why do you do project close out reports is so that you learn and adapt it for future use. (Learn out of our mistakes and implement corrective action).



What is the critical Path. The Longest Path. (Please note float is not part of my definition of the critical path because sometimes you do not calculate the float) “concept similar to float “ is still not float.



Even a Project with no schedule have a longest path. (Even though nobody know about it) My apologies Gerry I did not read the practical part.



If a project does not have a longest path we can assume that we can finish it overnight.



Maybe if you do construction planning the A.B.C.P. might not be useful but when you do project planning this data is. Besides the Q is Does an As Build CP Exist.





Cheers

For Line of Balance, although float is not applied, the game rule is similiar.

We plan for the optimum by shift the bars around; bar thickness and gradient of bars. The shift, thickness and gradient, on concept, is silimiar to float.

[Duplicate entry deleted.]

So if a project has no schedule it can be completed over night ????. No a Critical path is more than an calculation it is a fact of live.



If I make a decision to use a Line of Balance Planning (LMS) system on a hundred Kilometer pipeline I will not have a critical path because I can not calculate it due to a Line of Balance can not calculate float (No CPN).

I agree.

Critical path, besides it is defined as the longest path, is usually defined by TF=0. If no schedule, all the above is not exist and so, what is the measurment criteria?

Gerry,



Do you mean a critical path with logic links/relationships between activities; or a graphic presentation of activities showing what was critical to project completion at any particular time over the life of the project?



Roger Gibson

I understood that this discussion refers to contract schedule. In other case traditional critical path will not define project duration if resource constraints are taken into consideration. Resource Critical Path (or Critical Chain) takes its role and defines project duration.

Contract schedule may change due to the various reasons - delays, change requests, risk events, etc. Activity start dates may be delayed not in accordance with the schedule logic. Due to some events not necessarily the longest path will be really critical.

So if you want to be able to restore As built Critical Path all events that lead to delays shall be included in the project schedule with the corresponding links that show which original activities were delayed due to any event and which preceeded delay. Of course you may find critical path using Float less than, not just zero float.

If it was done during project execution then As Built Critical Path can be restored.

Hi Gerry



I still say a As Build critcal path exist.

Does a project without a schedule have a critical path.



If your answer is yes then you must define the definition as the longest path & forget about float. (remember the project does not have a schedule). (Differance between planning and scheduling)



Also have any of you used why before. Once you have completed a schedule ask yourself why was the project not finished earlier and then go through the activity’s one by one and ask why was this not finished earlier. Eventualy you will see the true as Build Critical path.







Cheers

Gerry,



Don’t you mean “I don’t mean to be critical but….” ?



Me ? Plan?

Couldn’t plan a piss-up in a distillery on Hogmanay!



Cheers,



Stuart

www.rosmartin.com

Hi Gerry,



My views have not essentially moved from that of my earlier posts; if anything, however, my expressions may have modified! I now accept (thanks to the clarifications offered by this thread) that the term “As-Built CP” is at best misleading and at worst entirely wrong! ;-)



Against the background of the clarifications offered by this thread, I would say that I haven’t changed my mind – just my words!



Cheers,



Stuart



www.rosmartin.com

Hi Staurt,



I don’t think there is a name for it so just call it the longest path:-) The point being that if the project finished early the longest path was never critical. Further if the project finished exactly on time or late, and the last activity was say "Handover", There would probably have been some other chain of activities linked to the final activity, so it might not necessary have been the longest path activities that forced thee project to end late. So again give one good reason for bothering with a so-called "As-built CP".



Regards,



Philip

Hi Staurt,



I don’t think there is a name for it so just call it the longest path:-) The point being that if the project finished early the longest path was never critical. Further if the project finished exactly on time or late, and the last activity was say "Handover", There would probably have been some other chain of activities linked to the final activity, so it might not necessary have been the longest path activities that forced thee project to end late. So again give one good reason for bothering with a so-called "As-built CP".



Regards,



Philip

Stuart,



I would call if the ’Actual Critical Path’. It is the sequence of activities over the life of the project that caused the completion date to be delayed from ’x’ to ’y’.



By using the ’windows’ or ’salami slicing’ methodology, (’windows’ sounds less painful Stuart)then this path is established.



Also, as it is often the case that an activity may be only be critical for part of its actual duration, I don’t know of any planning foftware that can determine and graphically show this from a final as-built project with actual start and finish dates for each activity.



Roger Gibson

Hi Philip,



Yes, I agree – which is why we should stay away from the term “Critical Path” insofar as an As-Built Schedule is concerned. What therefore, would you call the longest line of activities through an As-Built Schedule?

Isn’t this where it all began?



Cheers,

Stuart



www.rosmartin.com

Hi Stuart,



It is like magic, here today gone tomorrow.



The point is if an activity is complete it’s float disappears.

Very interesting thread (now that I have caught up with it!), and I think that we are mainly reading from the same page. I would agree with Roger and Gary about the “snapshot” or “windows” approach – personally, I stay away from the word “windows” to avoid confusion with u-no-what; I prefer to call it “sausage or salami slicing!”



Unsurprisingly, we all seem to agree that the CP runs forward to the end of the project (starting now or at some other point in the future) and we all seem to agree that the CP can multiply and can flit around from day to day. Ronald’s last post (!) emphasises this point. However, I am unsure as to whether this answers Gerry’s earlier question as to what you call the CP once it is consigned to history (i.e., what do you call today’s CP tomorrow when it becomes yesterday??) [Thank God no lawyers are taking part in this discussion!!]



In addition, from a claims entitlement point of view, I would just add that if your Baseline Schedule is itself incorrect and unreasonable (subjective definition anyone??) then the formation of an As-Built Schedule that emanates from said Baseline Schedule, will itself be incorrect.



Cheers,



Stuart



www.rosmartin.com

[Duplicate posting deleted.]

Hi Sigfredo,



What you say is true. There is one thing however, that is a useful tool, that is saving the history after each each update. P3 has this feature in store period performance. Using this feature has two advantages, one , in that S-curves and histogrammes give a better reflection of actual events, and secondly, where delays occured they can be tracked correctly in the the event of a claim. The value of stored period performance is obviously dependent on the frequency of updates, the more frequnt the updates, the more accurate the stored information. One of the biggest and serious causes of productivity losses is disruption of activities.



Regards

Philip

what about coding the critical path networks say cpm1, cpm2....(the ranking of numbers 1, 2 will be based on the longest critical path compared to the next and so on....) in the baseline program itself so that it would be useful for monitoring the changes of critical path if any during update period and that can be used for tracking as built critical path if it exists so.

Hi guys,



Just want to share my ideas on the subject.



1. It is a fact that a Critical Path(CP) today may not be the same tomorrow, next week, next month etc. Unless someone will dispute this fact, please feel free to discuss it.



2. In comparison, as built CP is not the same as as-built drawings. As built drawings can not change meaning if a foundation size on the original plan is 2mx2m and it is actually built at 2.5mx2.5m, no one can dispute that what was constructed is a 2.5mx2.5m foundation because you can easily prove it. In As-built CP it is ever changing. What you may have as an as-built last week may not be the same tomorrow.



IMHO, I believe the word As-built CP is not the most appropriate term. I think History of Critical Path is the better term.

Hi Jaco,



The commonly accepted definit1on, of a critical path is a chain of activities with total float of zero or less, you can decide whether you want to increase the figure to more than zero, if I am working in days, and dependent on the overall duration of the project, I might increase the criticality to up to a week. The reason for this is to be able to spot all activities which is problematic, or might become a problem. You can also say that it is the longest chain of activaties in the project, however this is not always true, as the longest chain might be ahead of schedule, and another shorter chain might go critical, because of intermediate completion dates, resulting from commissioning procedures or other constraints.



Regards



Philip

Hi Phillip



Can you please supply us with your definition of the Critical Path.



Thanx

Hi Ronald,



I already mentioned the point about the critical path moving, however, I understand the project in this instance is already completed, hence "as built". If it is partially completed, yes there will always remain a critical path , and if it is behind schedule you may even have two or more critical paths, and in the instance where the project is well ahead of schedule, the critical path can disappear.

In my experience one of the best ways of analysing a completed schedule is by looking at the costing data, ie performance factors. When I speak about costing, I mean using budget manhours against each activity, and recording actual (clocked) manhours to calculate performance factors.

These performance factors can be plotted against time or % progress, or for individual phases or discplines for the project. If you look at these curves, it will help you in future projects of similar nature to adjust budget estimates, which in turn will give you a better idea on how to work out durations. I have found this a valuable tool in the past where we repeated the same job twice but reduced the duration of the second project by twenty percent.



Regards



Philip

The "Critical Path" extends from "Today" (the data date) to the end of the project. Due to the dynamic nature of daily CPM activity, the critical Path can switch daily for one chain of activities to another and back again the next day. Each day, there will be a critical path (but not necessarily the same path.)



I am saying that the only thing that the critical path has in common from one day to the next is that ON THE DATA DATE, a certain set of activities were both critical and active. This is the only thing that matters. Note what was critical on any date. Add all of the dates together (one at a time) and you have a list of critical, active activities. This is the only truth.



The daily critical ’path’ may hop from one chain of activities to another without a logical relationship between then to ’model’ it. The ’critical path’ may actually hop between two or more activities as they progress. It does not matter. Each and every day, something is critical and active. All of the rest is either unknown or planned.



Don’t focus on one single critical path. Instead, focus on what was critical and active on any given day. The difference between the two is the difference between classical CPM theory and the truth.



Ron Winter.

Jaco - Yes, you can compute the CPM for completed activities but do not forget that the CPM is computed using activity remaining durations. The remaining duration for a completed activity is zero. This does not tell you much about the critical path in the past.



Philip - You are correct ahout ’hindsight’ but what about ’Today’? You can certainly tell what is critical today. Tomorrow will eventually come and when it is ’today’, you will be able to determine the critical activity for that as well. My point is that for any given date, you should be able to state what was critical for that date - even for dates in the past. I have not said anything about the Critical Path - only the critical activity for any given date.

Hi Gerry and others.

I have been watching this discussion with keen interest.



My opinion is, on the question that Gerry originally asked, is that there is no thing such as an as-built critical path, simply because if something is complete, how can it be critical? ie Hindsight is 20/20 vision. Anybody trying to establish the critical path in retrospect did not do his/her planning properly in the first place. Further, the critical path will not always remain in the same chain of activities. If Gerry is working on a claim, any tampering with the original and as-built programmes would make such programmes nul and void, as back-up material in the claim.



Regards



Philip

Hi Ronald



I was looking at your paper and was wondering why can’t you calculate Float on activity’s that is completed. Remember you can change the dates to Non dates (numericals) even though computer systems don’t calculate float in activitys that is in the past you as a person can calc it manual.



I know actual should not have float but to do an as Build Critical Path you must calculate the float manual.



You can do a forward and a Backword pass on actual start & finish dates



Cheers

I have no qualms on explaining myself. Take a look at my Published Articles Section http://www.ronwinterconsulting.com/published.htm of my website. There is a listing there for, "AACEi 2004 Annual Conference: How to Manually Determine the As-Built Critical Path." It is a later version of the paper that I delivered at the conference. They let me live after presenting it, so it can’t be too far off.



Ron Winter.

I believe that the secret to understanding the type of network that you describe is to look at a re-computed CPM on a day-to-day basis. Start from the latest date, move the data date back one day, adjust the remaining durations of each active activity to reflect the actual work days remaining and re-compute the CPM. Then note which activity (or activities) was critical and active that day. Repeat this process, moving the data date to one day earlier until you reach the start of the project.



This is the algorithm that we use for a software product that we call “As-Built Critical Path.” It is a part of the Schedule Analyzer Forensic series. You can see more at http://www.ronwinterconsulting.com/forensic_main.htm. I also presented a paper on performing this algorithm manually at this year’s AACEi Annual Convention. You can find it somewhere under http://www.aacei.org/.



Ron Winter

[Duplicate entry deleted.]

Hi Gerry



Please Explain



Is it not the case that the piecemeal working and intermittent effort upon the activity (especially the kind of activities that Jaco mentioned earlier) seriously compromise the insertion of logic into an *as-built* programme.

Dear all,



This has become a very interesting thread. I would like to return to something that Roger Gibson said earlier. Assuming that Gerry is undertaking some sort of a delay analysis, or is preparing a claim, then that is why he is considering an as-built critical path approach.



In so doing, Gerry also needs to consider what Roger described as the “windows” approach. I concur with Roger, in that it is my preferred method of analysis as well. The reason why is this…..



In producing an as-built critical path programme, you can see what was the longest critical path chain throughout the project as it was at the end of the project. This is fine, but it lacks one vital consideration. The problem is that it considers the project only after it is completed looking back, but ignores what was known about at the time. Let me give a very simple example. Let’s say a house is being built and there are problems with building the foundations. The design is late and this causes a 3 week delay. This is on the critical path and an extension of time of 3 weeks is quite properly given. All quite straightforward and simple.



However, the design also incorporates a swimming pool in the garden, which is a contractor designed item. At the time of granting the extension of 3 weeks due to the late foundations, the swimming pool excavation is on programme and all seems okay with the pool. But, the contractor takes far too long to design the pool and order the water treatment equipment and this turns out to be the eventual cause of the house being completed 10 weeks late.



So if a retrospective as-built programme was drawn, it would show the as-built critical path going through the swimming pool, but not through the main house foundations.



Would you say that this as-built critical path programme was correct? It does, quite correctly, show that the eventual critical path went through the swimming pool, but some would argue that it would ignore the true cause of early delay – the house foundations. This is where a “windows” approach is preferred by some courts, because the windows approach, as Roger has stated, considers what was critical AT THE TIME. This is the important point. An as-built critical path can only consider what eventually turned out to be critical, but doesn’t consider what was known about at the time.



So, Gerry will have to bear this in mind when (if) he produces his as-built critical path. There are drawbacks to this system, as there are with most.



Gary France

Chairman

Planning Engineers Organisation

Hi Gerry



Yes it is Practical to do an As Built Critical Path on these Items.

Your Critical Path Should be something like this

From Back to Front.

1) Building Handover

2) Commision BMS - SAT -BMS FAT BMS - Development BMS -

2) Commision HVAC

2) Commision Fire Detection

2.1) Commision Permenet Power (LV) - Delivery MCC - Delivery UPS etc

2.2) Commision Permananet Power (HV)- Delivery Transformer -Delivery Switchgear etc

2.3) Power Supply Available

3) Installation of Controls Instrucments

4) Installation of HVAC - Delivery HVAC-Order HVAC

5) Access to Install HVAC

Your other activitys should run Concurrent.



Please note this just to give you some ideas.



Cheers

I think Uri is right in general to make As built critical path Schedule. But if you want to keep As built Schedule for future reference of planning then we should consider only those delay points which generally happens in project to identify the critical path. I mean to say that if the delay something like unavailibity of fund or vendor’s bankrupt comes on critical path we should ignore that to say that is not the critical path even though that will be longest path. Then we can say second longest path is really ctritical for future reference of planning but for cliam purpose the longest path will be considered.

There are two issues here:

1. The legel issue

2. The programming issue.



When analysing delays, the first place to look at should be the CONTRACT. Only when there is a reference in the contract to actual delays to the date for PC, the As Built programme becomes relevant. The Critical Path then would be the longest path in the as built programme.



In most cases the As Built Critical Path is not relevant, since the analysis is carried out RETROSPECTIVELY. The as built programme is used only as a record of actual dates, and not as a real programme with float, links etc.

Gerry, re your question: "Can a true as built critical path be created?"



I hope so, otherwise I have wasted much of my working life!! (not an entire impossibility, I grant you!!) ;-)



Cheers,



Stuart



www.rosmartin.com

Yes, critical path is most commomnly used term in planning and also it is the longest path based on the correct logic whereas "As Built Path" is not commonly used and not depenable.