Critical Chain Scheduling

Vladimir,



I agree, it is common sense. But our laws and their interpreters have an absolute lack of it; they have about 0% (+0%/-10%). They are so concerned about the technicalities they erased common sense from their vocabulary, blame on the legislator (partially agree) and twist the intention of the law.



I beleieve it can be done in our contry if private institutions take the lead and promote contract specifications that will benefit all. Similar to what some English institutions are doing right now. Of course I don’t mean to say these should be applied across the board to all jobs although I believe should be the norm in private and government contracting.



Best regards,

Rafael

Hi Rafael,

in our contracts we include the sentence that the contractor can do and finish the work ahead of approved schedule and this does not require the Owner’s approval. The Contractor has the right to submit the results earlier. The payment schedule and conditions are defined separately. So early submission of project results may lead to delayed payment only.

I think that if necessary conditions will be included in the contract all sides will benefit from better management.

I don’t know if it can be done in your country.

Best Regards,

Vladimir

Vladimir,



Critical Chain is based on buffers to hide true float, it is a lie the smart and the not so smart will soon discover and then you will get the “here comes the wolf” natural reaction.



I wanted it as a mean for getting our contracts and CPM specification writers to accept the fact that schedules are un-deterministic, that we should be allowed to target for early finish in the hope of finishing on time, unfortunately, at home, the schedule has been stolen away from the contractor and its main purpose have become for it to be a tool to manage change orders. Even with this reality in mind, after re-thinking about it I came to my own conclusion;



…”Why lying to your people and lose control of the schedule. Better keep several versions of the CPM, one for controlling the job and another one for the Owner. If you are to lie then it is better lying to the Owner, but not your own people. He is the one that insists in telling you how to control the job and usually is backfiring against all parties”.



For these M.F.krs at home, reserving some float as a buffer for the Contractor is not enough, they want it all. The argument that float belongs to whoever uses it first is wrong, is abusive, but is a standard clause in our contracts. I believe that at least some percentage of the total job duration, say 15% shall be allowed for the use of the contractor as buffer.



At home we have a need to keep track of several versions in a way that allows us to use common updating data in all versions and then, update each version unique updating data, this without getting into the statistical theory and all extra granularity of Success Driven Project Management methodology. I believe this can be easily done by using the functionality to import performance archive from other project. Will discuss latter in our giga thread "Lets Challenge Spider".



No doubt adequate scientific determination of total buffer can be determined with Spider Risk Analysis functionality. But for our small or medium sized jobs this is enough, and yes I know it is at a click of the mouse once initial setup is done, including all extra metrics you can get for trend analysis.



You have no idea how much I wish the concept of reserving some "adequate" float for the exclusive use of the contractor can be accepted here. Until then it will continue being a dream. Meanwhile showing Early Completion will continue to be banned by our specs.



The followint extract provides the reasoning of some Owners with regard to showing Early Completion in your baseline:



SUBMISSION OF THE EARLY COMPLETION NETWORK FOR APPROVAL



One of the things most capable of raising the ire of an owner is a contractor that submits a schedule for approval which provides for an early completion to the project. Courts have long held that where the owner causes a contractor’s performance to extend beyond the contractor’s planned completion date, the owner may be liable to the contractor for damages, even though the contract may be completed before the contractually specified completion date. The damage the contractor suffers is the loss of the benefit gained by completing the project prior to the scheduled completion. These damages are measured by defining the contractor’s per diem costs in awarding the contractor delay damages equivalent to the time performance was extended beyond the early completion date. See, e.g., Metropolitan Paving Co. v. United States, 163 Ct. Cl. 420, 325 F.2d 241 (1963); Maurice L. Bein, Inc. v. Housing Authority, 157 Cal. App. 2d 670, 321 P.2d 753 (1958).



There are a few potential answers to this problem. First, the owner may simply decide to discourage early completion efforts by calling out in the specifications that any submission, coupled with subsequent approval, of a contractor schedule showing an early completion will have the effect of moving the contract completion date to the earlier date, which will be the new point for the assessment of liquidated or actual damages. Another approach is simply to refuse to approve a schedule calling for early completion, so long as the owner can establish that the submitted schedule does not reflect a reasonable plan for performance. See, e.g., Sierra Blanca, Inc., ASBCA Nos. 32161 et al., 90-2 BCA ¶ 22,846 (1990). Finally, the owner who receives an early completion schedule about which it is concerned, but which it is not prepared to state is clearly wrong, may wish to consider the following course. First, indicate doubts about the reasonability of the proposed early date. Second, indicate that the owner will have to change its economic position to accommodate the early date (assuming this is correct). Third, advise that the owner will suffer damages if the early date is not met, because of the change in position. Finally, note that if the contractor wishes the owner to approve the early date, written confirmation must be provided acknowledging the contractor’s liability for any damages incurred by the owner’s change in position in the event the early date is not met (or adjusted for any time extensions). Importantly, courts have recently found that approvals of early completion schedules will be thrown out if the underlying schedule is based on unrealistic logic and durations. See Neal & Co. v. United States, 36 Fed. Cl. 600 (1996), aff’d 121 F.3d 683 (Fed. Cir. 1997).



Best regards,

Rafael

Hi Mal,

even in Critical Chain activities may have floats (postponing activity starts).

I don’t agree with CC proposal to add feeding buffers just for protecting Critical Chain. I don’t understand Critical Chain with hollows.

Though many ideas that are used in Critical Chain approaches are reasonable Critical Chain scheduling makes sense only for manual management of small and simple projects.

Best Regards,

Vladimir

Jonathan



Critical Chain is not just a planning technique. To make it work in its true form you need to educate your project team in how they approach planning and activity management.



To develop your programme, you must agree you task list, logic, a most likley and focused duration (focused duration is the minimum time required to complete the task), resources etc. CC methodology discourages multi tasking for resources. From this you (the software) will calculate the Critial Chain (ie the critical path, but based upon logic and resource loading, a project buffer (a time period at the end of the programme) and a number of feeder buffers for tasks not on Critical Chain. Activities do not have float is the CPM way, all "float" is collected in the buffers and buffer durations calculated by the differnce between the focused and most likely durations.



Once your programme has been agreed/baselined. The updated process centres more around remaining durations and does not take into account percentage complete (not as bad as you think). Fore each task its "when did you start ? How long left ?





Loads of stuff on the web about it!



Regards



Mal

Hi Jonathan,

Buffer is not the Float.

Project buffer usually is created to accumulate contingency reserves that shall not be spread along the project and included in every activity duration estimate.

Critical Chain scheduling has no sense to me, but using buffers is necessary for proper risk management.

We use Success Driven Project Management methodology that combines traditional scheduling, risk simulation and using buffers for many years. If you want to learn more about this look at http://www.spiderproject.ru/library/cchr.pdf

Best Regards,

Vladimir

Hi Jonathan



Why not use the search facility to look up all the entries on Critical Chain.



For instance one thread from Vladimir reads:



"We use the approach that is similar to Critical Chain for many years (long before Critical Chain was invented by Dr. Goldratt). It includes RCP calculation and creating amd managing project buffers basing on risk simulation. Unlike Critical Chain approach for buffer management we use buffers not only for time but also for cost and materials.



I suggest to look at http://www.spiderproject.ru/library/tt.ppt and some other papers and presentations at http://www.spiderproject.ru/publ_e.php#eng"



There are many more like this already on the PP forum.



Best regards



Mike Testro