As Built Critical Path

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

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.

Topic Reminder - Does an As-Built Critical Path exist?

Jaco - to answer your earlier posting - "Does a project without a schedule have a critical path?"

My PRACTICAL answer is no.

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 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?

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).

[Duplicate entry deleted.]

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.

Jaco

That is why I emphasised the word PRACTICAL in my response to you. A project with no schedule/programme has the potential to have many many critical paths. Of what use is this information? Think of the purpose of a CPA (before the job is built). It is to enable managers to focus construction effort AT-THE-TIME.

It is trite to state that even a project with no programme has a critical path.

As for you concluding that a programmme with no schedule can be completed overnight - You’ve lost me there. I never inferred such a daft notion.

Gerry.

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

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).

Vladimir

The real question is to focus upon the retrospective insertion of logic into your as-built schedule. Is it appropriate?

Gerry.

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.

Vladimir

What do you mean by Schedule? Especially when you state

"Why does everybody agree that there is not such thing as an As Built Schedule?"

No-one is disputing there are as-built facts. In your mind (and others reading this) does the word ’Schedule’ (in Vladimirs context) imply logically linked as-built activities - or simply activities that have been built (i.e. undisputable facts).

Gerry.

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.

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

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.

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

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.

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!

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!

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

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.

Vladimir

Consider Philip Rawlings item (e)

(e) Above all, remember that the CP is not factual. It relies on a subjective assessment of the relationship between activities.

How can you disagree with this? Especially if you are dealing with anything other than very detailed programmes.

You make the point that CP is usually based on "technological restrictions (roof after walls, etc..) If only life was that simple. At the beginning of many design and build projects construction detail does not exist. The activity bars are long and have long overlaps. The logic is (and must be) subjective.

Even with a roof after walls scenario - the leads/lags have subjective durations.

I agree with Philp - the Critical Path (prospective) is not a fact, it’s an opinion. The Critical Path (retrospective) well, that’s a different story - one which there is much disagreement upon within this thread.

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

Hi Gerry,

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

Phweww.. and what a wait!

Philp - Do you fancy formulating a useful question for the vote? I think "Does an As-built Critical Path Exist?" is too simple as the unfortunate answer is likely to be "It Depends".

Gerry.

Gerry
Just look it is next to the Elbow Grease.

Maybe the only useful question is:

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

Sorry Philip Rawlings, my question was directed to Philip Jonker.

As for its purpose (ABCP) - Billions of pounds/dollars are fought over every year in Extension of Time Claims and the notion of an As-Built-Critical-Path is central to many of these disputes.

Just look at the first three quarters of this thread to flush out the views that Planners hold.

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).

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

Philip(s)

I think your suggested phraseology for the question is just a wee bit loaded and it might just betray your answer!

Thanks for your input, it has been a good thread.

Gerry.

"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

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’

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

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

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

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

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

Vladimir

Critical Path is reliant upon a forward pass and a backward pass in order to determine earliest and latest dates for the activities. Where to actual dates (i.e. in the past) fit in? In the past there is no earliest or latest dates, there are only actual dates. That is Philp’s point.

Gerry.

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

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".

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

Gary,

Do you use your as-built-critical-paths to undertake substantive collapsed as-built analysis?

Gerry.

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?

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

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

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

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.