Critical Paths - Are they all theyre cracked up to be?

Hi David,



Charlie (applied to irregulars or guerillas not the contributor to Planning Planet) is a leftover from the Vietnam War. It comes from the NATO Phonetic Aphabet table Victor Charlie - VC - Viet Cong.



Chris

funny that isn’t charley the term they use for guerrillas

Oh yes, forgot possibly fraudulent misrepresentation in the last post as well.

Lots of interesting points raised here. Ironically I posted a similar message in another post yesterday. First and foremost a programme is a tool for the management of the project.



Fail to plan properly, plan to fail.



The programme should be as accurate as knowledge and time permits. I agree it is often the case that the time given to produce a programme or the information available falls far short of what is needed. But this is still no excuse for not producing the best you can at the time.



As for manipulating the critical path, if you do this the programme is not worth the paper it’s printed on so doesn’t fulfil its intended purpose. May as well throw it in the bin.



It’s also embarrassing and not good for your career when someone else gets to scrutinise it in a later dispute to be told and shown that you were wrong, your effort was obviously flawed and that you misrepresented the truth. I would suggest that such manipulation actually falls far short of the standard expected from a professional planner and at least amounts to wilful deceit, possibly negligence.



My advice to all planners is to do what you’re employed to do – plan the job. This way the project has the greatest chance of being successful and everybody is happy.

Gents - a very interesting debate, highly emotive, but has been somewhat hijacked by invective.



Notwithstanding the fact that each party has put forth valid points of argument, we must begin to use language that becomes more precise in terms of its defintion. Apologies if the next lecture is granny-sucking-egg.



First: we must not confuse the word EXACT or PRECISE with the word ACCURATE. Any numerical manipulation, using the input variables, as derived, will arrive at an EXACT or a PRECISE value. However, the variables that form part of the equation determine the potential ACCURACY of the result - as comparing the theoretical result with the actual result. Perhaps to help understand the word "accurate", here are some definitions from the American Heritage Dictionary.



ACCURATE : adjective.

Conforming exactly to fact; errorless.

Deviating only slightly or within acceptable limits from a standard.

Capable of providing a correct reading or measurement: an accurate scale.

Acting or performing with care and precision; meticulous: an accurate proofreader.





Now you can start fighting over the definitions!!



Charlie is right, in that sometimes you have an extremely limited time to prepare a large schedule. The reasons for time-limitations are irrelevant. The real-life fact is that it often happens. However, the method by which the critical-path is calculated will (should) still be the same, and will continue to derive a precise value, but the "accuracy" of the schedule will be compromised. Spending 5 months on compiling a schedule will also give you a precise value - but it may not necessarily be significantly more accurate. As usual, a balance has to be struck.



The planner’s job isn’t helped by the fact that the "result" can be manipulated via interpretation of the initial input variables, thus giving the client the result that he would like to see, as opposed to reality. We’ve all been there, and know full-well that, if we told the client the real cost of the job, we wouldn’t get the job. Moreover, we could all philosophise about the rights-and-wrongs of "data manipulation" via interpretational liberty.



James.

Hi Clive,



Strange that you should go back and look at one of Charlie’s earlier posts, I’ve just done the same, post #47 where he was going on about the second world war and using that to take another of his little digs at the English.



I did notice though that he rather got things wrong. The defences for Singapore were commissioned under the 1935 defence estimates and were in place by 1937. At the time they were a response to a percieved threat, but at the time of the Japanese invasion it was known that these defences would not be effective. I’ve no doubt Charlie would ask, "Well why didn’t they do something about them then?" Possibly because at the time Britain was rather busy in Europe, and the resources simply weren’t available.



Another interesting point is that Charlie points to MacArthur saying "For the second option, MacArthur organized guerillas to continually harass and slow down enemy advance." That is incorrect. Early in 1942 MacArthur asserted that guerilla operations were impossible in the Phillipines. The Guerilla operation in the Phillipines was initiated by a remarkable man, a Lt Colonel of engineers called Wendell Fertig. He promoted himself to Brigadier General and organised a resistance using Filipinos, escaped POWs and troops who had remained behind.



MacArthur at first tried to ignore Fertig and his efforts, but they were too successful, but it wasn’t until 1943 that MacArthur actually started to supply the guerillas with arms and equipment and to claim that the whole thing was his idea.



I don’t propose to say too much more other than to suggest to Charlie that if he is going to pontificate, he should at least get his facts right.



Chris Oggham

Hi Clive



Sorry for another comment. I belive, it’s a waste of time to discuss with a person who is sure that a science - mathematics - is no science, but only his expert knowledge - you used a beautiful picture : "..presenters will have among them a tin man, lion, scarecrow and a pair of very red magic shoes".

But you are right, juniors may be misleaded.

Joseph wrote "The schedule as per contract shall be submitted within 30 days after signing of contract" and he tried to raise the impression that he created such a schedule within 30 days. This could only be achieved with the support of long haired ladies with a bowl of glass, dice, cards, watching birds or equivalent - it cannot be true.

I know such conditions as well. They are ok, because during the phase when you prepare your - serious - offer, you need a level-2 and for some areas level-3-schedule. This is not only essential for price and contract-milestones, but to check for feasibility as well. In general you have 3 to 5 months time to prepare your offer where the schedule is an essential part. Joseph obviously didn’t know.

Planning/scheduling is a serious job and does use scientific methods, even if much data is based on assumptions and/or personal estimations.



Kind regards to all



Dieter

I think I will just call in the artillary to cover me, whilst I try to implement the PINCER movement.



Just like I do with critical paths and turnips.

To my Peers in PP,



I will make an addendum. This refer to "exact estimates" compared to "Exact".



During the early days of World War II, the commanding general of the English army in Singapore instructed: gave me the exact estimates of the intent of the Japanese Army.



The reply: The exact estimate is that Japanese will make amphibious landing in Sentosa Island.



So to prepare for the exact estimates of amphibious landing by the Japanese all Guns in Sentosa pointed to the sea



The English army was dead wrong. The Japanese march through Malaysia and hit the English army backside. No guns where fired. Surrender without firing a shot.



Compare with General Douglas MacArthur.



During the early days of World War II, General MacArthur knows exactly where an enemy will attack to conquer Manila. There are two axis: the best option is to send naval vessel (with troops) toward Manila and the other options is to land troops in Lingayen gulf (Pangasinan) and fan out in the Central Plain of Luzon then march towards Manila.



To know exactly the enemy intentions, MacArthur fortified Correigidor, the small island at the entrance to Manila Bay, with Heavy Cannons. For the second option, MacArthur organized guerillas to continually harass and slow down enemy advance.



The Japanese first attempt was to go Manila through Corriegidor Island but the big guns of stop them. The Japanese land troops in Lingayen but the guerillas harass and slow down the advance to Manila. The impact is slow down the Japanese timetable of world dominance.



It is the same with Critical Path. We know that initially the Critical Path is not exact and it is only an estimated guess. As progress of the project moves, monthly update and critical path analysis shall be done to assess the movements of critical activities and critical path.



The point here is that what we are going to do after all this issue is blown out of proportion???? My preference is quite clear.



Cheers,



Joseph

Dieter/Oliver,



Charlie does indeed have the right to his opinion and if he wants to say "CRITICAL PATH IS NOT AN EXACT SCIENCE" then let him do so. Of course what people deduce about his personal expertise based upon that statement is entirely up to them.



Charlie says that the judge in Mirant vs Arup also agrees that CRITICAL PATH IS NOT AN EXACT SCIENCE. Perhaps we should remember that a judge is an expert in the law and not project planning or management. I wonder what Charlie’s reaction would be if that judge looked at him and said he was in iminent danger of a heart attack? He would, quite rightly, dismiss such an assertion out of hand, the judge is not a medical expert. So why should anyone give much weight to what a judge says about Critical Paths?



Chris Oggham.

No additional comment from me.



Dieter

Charlie,



You are similar to the witnesses in the case.



’In this particular case a number of witnesses were convinced, without the benefit of any critical path analysis, that they knew where the critical path lay. That in fact influenced the decisions made during the project.’



We have the same opinion as Toulmin J.



’Toulmin J agreed with the Core Principle No.1 in the Society of Construction Law Paper that a properly prepared and regularly updated programme would reduce the number of disputes relating to delay.



He did however observe that it was possible to affect the critical path by giving some activities a longer time than was necessary, thus keeping them on the critical path and having the effect of keeping other activities from being on the critical path. This was an implicit recognition of the potential inaccuracy of any programme depending as it does on an estimate of duration of activities.’



Like we said since the thread began, CPM is an exact science, but its accuracy is limited by the integrity of the programme.



A thankyou...

Dieter / Olly,



Your opinion is your opnion. Good we have a democratic Planning Planet.



I exercise my right to say my opinion "CRITICAL PATH IS NOT AN EXACT SCIENCE". There is not need for you to agree with me in the same way that there is no need for me to agree with you.



This only show we are democracy.



Please take note that if you read Mirant vs Arup, the judge himself agree with me that CRITICAL PATH IS NOT AN EXACT SCIENCE"



I rest my case.



Judge, please the verdict.



Cheers,



Joseph

Hi Joseph

It is extremely difficult to discuss with someone who doesn’t want to listen.

Item was, if the critical path is scientific. Then you refer to that input is based on assumptions and so CPM cannot be scientific. Wrong! All scientific methods base on assumptions. What is better, make a novel out of a project, were based on your absolute knowledge you know the critical activities and the end-date or to let a software calculate and then evaluate the results? I experienced that especially in big projects I can’t rely on feelings, but on science + experience - well knowing: all is based on data from estimations and assumptions i.e "best practice".

Regards

Dieter

Charlie,



I mentioned nothing of language.



Critical Path ’methodology’ is an exact science.



Estimating is not an exact science.



Critical paths are formulated from forward and backwards passes to ’mathematically’ determine the critical path(s).

This relies on the estimating and logic being ’honest’, not ’manufactured’.



Maybe the heshe that taught you was wrong.(it would certainly explain a few things)



Kind Regards,



Oliver



P.S We didn’t lose the empire, we let people have it back.

Olly,



I heard this before when I was a small boy starting to learn english.



"Give me the exact estimate of ?????????? whatever."



We are not native born english speaker but we know that this is a wrong use of english.



I’m really sorry for you as a native born english speaker. You don’t know what you are telling the whole PP community.



HOW ON EARTH THAT YOU WILL HAVE AN EXACT SCIENCE WHEN YOU ARE DOING ESTIMATES. Is this accepted in the English Language.



Is my teacher wrong when he/she castigated me that such usage is not logical.



OLLY, are you an engineer. In England or UK they dont differentiate natural science like Newton Law of Motion against hearsay / estimates. Estiimates is an estimates. How come it will be exact.



My goodness what on earth happen to the new breed of englishmen. Maybe one reason you lost your Empire where the sun dont settle.



Im sorry for you;



CPM is an exact science based upon your best estimate.



Cheers,



Joseph

A critical path is the result of planning based upon estimates and educated logic.



Lets not forget the arguement is are they any good?



The answer is yes, if the duration and logic are based on reality.



The answer is no, if you try to force activities on to the critical path by changing logic and estimated durations.



The size of the project doesn’t affect how you arrive at the critical path, it only means that during progress the path may change more often.



CPM is an exact science based upon your best estimate. The baseline is the only thing you can compare against.

Dieter,



Have you done a scheduling for 3 Billion USD project with 30,000 activities that start from Design (conceptual, schematics, detailed desing or Design Concept 1,2,3 and 4) procurement of major machineries and long lead items, construction (infrstructures, buildings, utilities, mep, etc) testing and commissioning????????????????????



The schedule as per contract shall be submitted within 30 days after signing of contract otherwise a certain amount from the billing will be witheld until an approved schedule will materialize. Have you been in this situation before wherein failure of the planning engineer will result in marching order and flight back home to country of origin.



Do you think those planners will still arrive at critical path as an exact science??????????? Be realistic



I agree to construct small dog house for english bull dog, maybe, the critical path might be an exact science. The critical path for family planning can be an exact science.



But no way for EPC MEGA project in the oil and gas, building construction, etc. in the range of 10 Billion USD above.



Cheers,



Joseph

Hi Joseph



I reflected some time to answer to such an agressive post. Why do you think that you’ll have to follow that style. Was it because as you said in a previous post’: "I learn to live in reality since my idealism (also my youth) has long gone."

Ok, I am a scheduler and although I covered my 30years of business experience January this year, I like my job. Therefore still I am enthusiastic to work as a scheduler.

"So your if and then, opinion is irrelevant." This is no way for discussion!

That’s for your attacks against me.

Critical Path is an exact science! As an engineer you "I grow up eating numbers" that’s not mathematics.

I absolutely agree that a plan’s quality depends on the persons by whom it was created - and what’s for narrative reports, you like so much? For both you have a human input with all possibilities for error. The result in one case is absolutely unstructured with all chances for manipulation and/or personal evaluation the other is a structured result were all assumptions can be traced.



I would like to ask you a favour: Keep normal human politeness even if someone doesn’t completely follow your ideas.



Regards

Dieter



p.s. Did you ever plan a wedding? It’s a horror.

Dieter,



I’m an engineer. I grow up eating numbers, from arithmetic, mathematics, deferential calculus, integral calculus, engineering mathimatics, structural design, etc.



You can name what branch of mathematics you involved with



So your if and then, opinion is irrelevant.



You have to understand that the foundation of duration estimates is governs by the law of probability. Do you understand the Law of Probability.



You have to understand that the critical path will always be arrive by the links of activities as understood by the planner. As you are aware, a lot of planners call themselves planners just because they know how to punch the computers keyboards. And this is the reality.



Do you think the planner is not human subject and limited to his understanding not govern by the natural law of nature including the natural law of mathematics.



In conclusion, critical path will never be an exact science due to inputs by planners (humans), some hafl bake planners/ some only good as wedding planners.



Cheers,



Joseph

Hi Joseph

If you are sure that Mathematics is not an exact science, then you are absolutely right.

Critical Path is a part of Graph Theory, which is a part of Mathematics. Main algorithm developped by Dijkstra in 1959.

If you work with manipulated length, any algorithm will follow GIGO principle - Garbage-In-Garbage-Out. The result will be wrong. But if we work with best practice assumptions, there is a big chance, to get a correct critical path.

You are right, real life sometimes is different: Last week I received a nice "schedule" with no relation, but "critical activities". It wasn’t a joke!



Regards

Dieter

Clive,



I your example regarding car assembly, this is operation. The culture of operation is different in project.



Project is unique.



I agree with your example with concerning our industry. Construction generally are projects. Even how much we learn from previous experienced, projects are still unique.



But what we really needs to focus is project management best practice. On planning side, the Mirant vs Arup case give us lesson learn on the way we treat Critical Path.



For example, what jusdge XXX notice is that while the argument focus on critical path, one sub con ZZZ did event bother to update schedule. So strange????



When I workd, I always insisted on a narrative of the critical path. How the critical path change, why, how come, etc. Then this scenario will be betted by senior management on how they feel



I did this now that I’m the project manager. But there are resistance because we planners are experieced in different background, educational attainment. nationality project culture, etc.



I learn to live in reality since my idealism (also my youth) has long gone.



But, you reference to Marant vs Arup, is an ammunition to me to convince my superior that we do need to monitor dritical path (including manipulation of critical path).





Cheers,



Charlie

Hi Clive,



Critical path is really not an exact science.



It is very easy to tweak an activity duration longer than what is necessary for critical path to pass the said activities. This will hide those suppose to be critical activities. This is one reason that Senior project team member must supervise the works of Junior team members considering that Senior citizens of the project team have wisdom on how project implementation will proceed.



What we have to note is that CRITICAL PATH analysis is very important in Calims for Delay.



I thank you for your referal of the post below with regards to Mirant VS Arup.



Since critical path is not an exact science, then it need to be monitored perdiodically, preferablly, monthly basis. We know that during monthly updates, some critical activities will no longer become critical. There is a shifting of critical path. And this need to be analysis on why this is so, how, what, etc, etc.



What I’m trying to say is: The importance of critical path analysis on delay claims.



and, I hope you agree with me.



Cheers,



Joseph

or an ashtray on a motorbike.

Are we forgetting that the "Programme or Schedule" is only one tool in the project managers armoury.



Have any Planners here utilised Last Planner Techniques.



In my mind the programme is the road map, it cannot be used stand alone.

Support the programme with sequence diagrammes sketches anything to get the message accross.



The important thing is to ensure the men at the "coal face" have the tools and resources when they need them.

Hi Stephen,



Refer to your original post no. 1.



A planner usually do the best he can in the preparation of work program or schedule. This is dependent on his academic background, if the planner has one and his actual field experience.



For Junior planner, generally the work schedule will be commented by senior planner. And this is why you ask the question if critical path are cracked up.



For experienced planner or project managers, the critical path can be easily determined dependent on project location. That is why you sometimes questioned if critical path are cracked up.



Your problem start when people start to questioned the way you prepare you program including critical path.



Cheers,



Joseph

Hi Clive

Just read those parts of this article related to critical path. For my opinion it is an excellent support for our work - especially against those

- Who are convinced to know critical path from the beginning

- Who ignore the importance to schedule a project regularly inclusive a given forecast on basis of the actuals and to keep regular baselines (the complete project!)

- Who ignore the importance to "stay on the ball" as a project manager, i.e. regular and frequent updates of progress.



Thank you for this link although it was hard to read on early Saturday morning.



Best regards



Dieter

Well done Clive - my sentiments also.



We currently have a client who wants to prescribe so much that we might just as well ask him to construct the programme as well. He can then make it fit his own mindless milestone dates. All we’ll do is the work.

Hi Clive / Oliver / Dieter,



Please correct me, if I am wrong...



The intention when developing d program, shud b always positive. I wud like to use d word HOLISTIC approach while developing the program. Its absolutely true, that Client wants to expedite the project always and needs to be completed in a shortest possible time.



But, once the program is over, who would like to hear the comments from PM "I need to be that in this way, YOU SHOULD HAVE CONSIDERED ALL THESE THINGS"



So, involve Project Manager / Construction Manager right from the beginning while creating the WBS. We as planners, pick-up the duration and the relationships from the WORK METHOD STATEMENTS for all activities. These WMS’s are written/guided by them only.



We work on these durations and sequence set by the construction team. Don’t we?



So, being a planner, we develop the schedule and then find out the end date of the project. If it is going outside the clients requirement date, then we tried to pull it backward by using standard PM techniques supported by the project management software available.



Also, when we are actually CRASHING THE PROJECT, (may be because of culpable delays or as required by client in lieu of Acceleration cost), we FIRST DETERMINE THE ACTIVITIES NEED TO BE CRASHED and then start the scheduling.



Also, same principle follows during FAST TRACKING. PM/CM governs the activities need to be done with SS relationship.



In all the above cases, we follow the basic guidelines set by the PM/CM.



AND THEN THERE COMES, TO PREVENT UR OWN SKIN after such a HOLISTIC APPROACH



What the SCL SAYS,



Critical path analysis (CPA) and critical path method (CPM) - The critical path analysis or method is the process

of deducing the critical activities in a programme by tracing the logical sequence of tasks that directly affect the date of project completion.



So, ultimately we are NOT changing the project duration in either case. Just we are trying to be bit smarter than the person sitting on the opposite chair.



Hope I am clear this time?



Cheers,

Stephen,



Change control process.



It isn’t a EOT process.



Its up to the PM and client to decide whether or not the programme changes, its just sometimes easier to save up your changes for a re-baseline/EOT.



Oliver

How can you do it Raviraj’s way?



He mentions to extend the client activities? If they want a project expedited quickly then they won’t allow you to control the length of time it takes them to fulfil ’their’ obligations.



Self defence comes in the form of contingency in cost and time, this may inadvertantly change the critical path, but these changes should not be a foundation for the programme.



Such practices are why it costs so much to do so little. The whole point of project management and programmes in particular is to give a CLEAR representation of the intended obligations of all parties to help acheive the common goal.

Hi all,



In my experience, you seldom find

a team of PM + Client + Subcontractors + ...

without a "bad egg" of sorts, or more.



To cope with him or them, you more or less have to play

the game according to the way Raviraj describes it.

I would call it self defense?

Raviraj



Oliver and Clive are absolutely right. I saw many "planners" painting a schedule, predefining a "critical path" and later not realising a project running against a wall.

No, it isn’t a game, planning is a serious work!



Dieter

A GOOD planner plans the activities in a logical manner according the driving and succeeding matters associated with each individual activity.



Changing the durations of estimates and introducing false logic to doctor the critical path isn’t best practice.



Increasing durations makes projects longer and who is it that decides on the lengths of activities the client is responsible for?



Answer: The client.



There is a little thing called contingency which is used to help mitigate risks. If there is little risk, then their should be little contingency.



Mind games are for incompentant PM’s working in projects without trust.



Oliver

A good Planner before start of the program will definitely ask the CM/PM of teh project, what are teh activities / work packages, that need to be on the CRITICAL PATH, rather than following the CRITICAL PATH which is program generated.



That too is a sort of manipulation, but practically, it works!!



Ultimate need of the Client, is to have project on TIME.



Consultant / Contractor will just make sure not to be on the CRITICAL PATH, by increasing duration of the activities, for which opposite party is responsible.



Just a mind-playing game. But, it really works and who so ever is SMART wins the race!!



Cheers,



Raviraj

Hi Steve,



Just kidding. Wanted to have a fresh and relaxing mood after posting so many detailed & serious thoughts. Just tried to make everybody smile, with no intentions of hurting anybody. Sorry, if it hurts u.



Well, overall CRITICAL PATH doesn’t make any sense, as even delay in few activities in the start of the project, will change the CRITICAL PATH a lot. Thats y, d concept of AS-BUILT CRITICAL PATH (ABCP) is developing these days.



Being on the consultant side, i never keep activities, for which I am responsible, on the critical path.



e.g. Approval of technical specifications, Engg. submittals and drawings or weather award of Nominated Sub-contractor or Sanction of Provisional sum Items. Or even approval of samples, submitted by the contractor.



Never keep them on the critical path. I would give contractor some more duration keeping his activities on the critical path and having float for me.



But, if u r working on CONTRCATOR side, then its vis-a-vis. Try to put less gangs on a particular activity, say tiling works (for a Building project) and get d approval of Tiles much earlier. Say, if its a 60 floor building, then put two gangs instead of 6, and make approval of tiles much earlier. In this case, you got a chance to even put 6 gangs later gangs on site, if theres a delay from client and then ask for the acceleration cost.



Make more money is the basic intention of the BUSINESS keeping the stakeholders need as it is.



HOPE I m clear.



Cheers,



Raviraj

Steve,



In one way I agree CPM is not all it could be.



In theory it is excellent but in practice it only works with a flawless schedule.



And to get a flawless schedule isn’t possible.



Oliver

Blah Blah Blah.......



Stephen, have a KISS (Keep It Short & Simple)