Talk:Critical path method

Outdated by 25 years!
The arrow diagram shown in this article reflects a methodology (Arrow Diagramming Method) that has not been popular for more than 25 years! This is the kind of outdated, obsolete and useless informations that infects the Scheudling Practice. This page needs to be completely rewritten. As soon as I have time, I will put something up, for review and consideration.ICSGlobal (talk) 14:02, 22 May 2008 (UTC)

Changed back to version that includes AON diagram and critical path drag calculations
Hi, PM Master. I've been waiting about two weeks for you to get back and discuss your taking out the edits I made. Since you took out those edits within a day, I'm thinking that undoing your undo is the one way to get you back to discuss this. My previous message in this discussion below: Nuggetkiwi (talk) 13:05, 20 June 2011 (UTC)
 * Hi. The problem is that you are promoting a book, obviously yours.Pm master (talk) 15:11, 20 June 2011 (UTC)


 * Hi, Pm master. My intention was not to promote my book, but to include a key metric that adds significantly to the value of CPM: critical path drag.  I previously cited my book as a reference.  Since this is unacceptable (I'm not sure why, since there are plenty of other books referenced), I have removed all mention of my book.  My fear is that now someone who doesn't know about drag will remove it again.  If a reference is needed, I'll be happy to provide either articles or software packages that compute drag.  Thanks. Nuggetkiwi (talk) 11:52, 22 June 2011 (UTC)


 * Are there any third party references for this material, or is it solely used in your work? Kuru   (talk)  12:02, 22 June 2011 (UTC)


 * Hi, Kuru. First, let me say that I didn't create drag; it's there on critical path activities, whether or not we choose to compute it.  It's the amount by which a CP activity (or lag or constraint) is delaying the end of the project.  I just pointed out its importance (greater than float, since it costs both time and money) and how to compute it.
 * Bill Duncan, author of the 1st edition of the PMBOK Guide (1996), teaches it in his classes (http://www.projacs.com/training/course-search.html?course=367) and wrote an article titled "Scheduling is a Drag" published both at ProjectsatWork.com and as a PDF thru asapm.org, the US chapter of IPMA (http://www.asapm.org/asapmag/articles/DRAG.pdf). (Duncan was kind enough to credit me as co-author after I explained the concept to him, but he actually wrote every word). And in Joan Knutson's book Project Management for Business Professionals, Jack Nevison wrote an article titled Multi-project Management that says: "The helpful concept of drag on the critical path is explained in Devaux, 1999." (http://www.cin.ufpe.br/~gmp/docs/papers/Multi-Project%20Management_Executing%20the%20details%20of%20Project%20Portfolio.pdf). There may very well be other articles (I've been teaching this concept for many years both to large corporations who have been using it routinely to optimize and/or recover schedules, and in graduate classes). When I input "project management" "critical path" and "drag" to Google, I get 172,000 hits. Most are probably "drag-and-drop", but who knows?
 * In addition, there are now at least two PM software packages that compute drag: Spider Project (a major package and competitor of Primavera in Europe, Asia, Africa and S. America in the construction industry) says that it computes "Total Float, Free Float, Super Float and Drag". (http://www.spiderproject.com/index.php?option=com_content&view=article&id=15&Itemid=10). Additionally, someone named Peter Mello who apparently is associated with Spider's Spanish team has a blog about it. I don't read Spanish but maybe you do (http://petermello.blogspot.com/2009/09/pmi-sp-caminho-critico-tem-folga-o.html).  Sumatra.com has an add-on to MS Project called the Sumatra Project Optimizer that computes critical path drag (http://www.sumatra.com/projectoptimizer/projectoptimizer.htm).
 * But I assume you know CPM -- read the Duncan article, or my own "Drag Racing on the Critical Path" at ProjectsatWork.com and I think you'll see it's importance. Nuggetkiwi (talk) 20:26, 22 June 2011 (UTC)

Hi, PM Master. You edited out my changes, including an activity-on-node diagram, with total float and critical path drag computations. I placed the following message on your Talk page, but haven't gotten a response (admittedly it's only been three days). I appreciate the difficulty of your position, but I really would like to discuss this with you. Here is the message I posted to your talk site:

Over the years, I have uploaded quite a bit of material to Wikipedia, including but not limited to the PM pages. Most of this info is still there. One issue that has always bugged me with the Critical Path Method page is the (obsolete) AOA diagram (other contributors to the page over the years have also criticized this). So yesterday I spent several hours creating and uploading a PNG file of an AON diagram. I included not just float, but critical path drag computations, based on my book Total Project Control (John Wiley & Sons, 1999) and on an article by William Duncan (author of the 1996 PMBOK Guide), both of which I referenced. Drag computation is an important addition to critical path quantification, and there are even software packages that compute it. You removed the article with a comment somewhat to the effect of "Don't advertize your website." Believe me, my goal is not to advertise either myself nor my website (which was not mentioned), but to promote better project management (a cause that I believe is aided by the Total Project Control methods in general and critical path drag computation in specific). Drag exists on every critical path -- one can choose to ignore it, or to compute and manage it, but it's always there. Computing and managing it can lead to shorter and more efficient schedules, more targeted schedule recovery techniques, and money saved (and in certain applications, lives saved). I am happy to have my name, as well as the names of my book and articles, removed from the page -- I included them as reference to show that there is a published record. There are many organizations using these techniques, and PM software packages (with which I have no financial arrangement) that compute drag. You seem like an eminently reasonable person -- please tell me what changes I could make to my edit that would let you allow inclusion of the critical path drag computation. (Also, I really feel the AON diagram is an important inclusion.) Thanks, NuggetKiwi. — Preceding unsigned comment added by Nuggetkiwi (talk • contribs) 15:25, 7 June 2011 (UTC) Nuggetkiwi (talk) 20:23, 10 June 2011 (UTC)

Someone Else's Comment
131.110.83.17 16:42, 4 January 2007 (UTC)The statement critical path has no float is not correct. Critical path is defined as "the longest path through the network with the least amount of float. The critical path can contain float. But, it contains the least amount of float.

Linked the term "critical path drag" to a new page of that name with a more in-depth description of the concept. Nuggetkiwi (talk) 19:45, 6 December 2012 (UTC)

I disagree
A better definition of critical path is: the longest path of interdependent activities in a schedule network, whereby if any activity on the critical path is delayed by a certain duration, the project completion will be delayed by the same duration.

The critical path will be the path with the least amount of float, but many experts believe the critical path of a schedule should have no float. While it is possible for a critical path to have float, such float is most likely the result of a project completion constraint (i.e., a "Must Finish" constraint) in the scheduling software, which will give a project that is ahead of schedule postitive float and a project that is behind schedule negative float. —The preceding unsigned comment was added by Pkurtross (talk • contribs) 19:28, 14 May 2007 (UTC).

Kantian Origins?
I am in no way a management expert, but If I'm not mistaken, the whole notion of "critical path" originated as a concept in philosophy, in Immanuel Kant's Critique of Pure Reason. If that's the case -- and if this isn't a matter of the same term being reinvented for use in an entirely different sense -- it really ought to be mentioned here. --Michael K. Smith (talk) 03:28, 6 January 2008 (UTC) This topic is missing images or graphics, it's almost only text. —Preceding unsigned comment added by 85.171.132.202 (talk) 12:38, 17 April 2010 (UTC)

Downright awful
This was obviously written by someone who doesn't have a clue about either CPM or Critical Path Analysis. CPM was initially developed as a computer program. I'll try to come back and rewrite. I suspect this piece of garbage was put together by someone who had just completed their first PM training course. (Bill Duncan, PM Partners) Wrduncan3 (talk) 19:56, 16 April 2009 (UTC)

Timeline of CPM & PERT Development
The Thayer book cited in recent revisions to this article contains transcripts of interviews with DuPont personnel from the 1940s. One of these suggests that DuPont at some point shared CPM concepts current at that time with the Navy. This calls into question the independence of the development of PERT. However, Kelley, who worked on the UNIVAC implementation of CPM, was not aware that DuPont may have shared CPM with the Navy. Kelley was, afterall, with Remington Rand, not DuPont.

It should be understood that the timeline for development of CPM concepts extends much farther into DuPont's past than has been generally known. Again, the Thayer reference supports this view from the perspective of first hand participants with it from the 1940s. There are differing claims by those interviewed by Thayer regarding what CPM was actually called in the 40s. It seems most likely that Kelley and Walker did indeed adopt the term "Critical Path" from the PERT team. In fact, Kelley & Walker say as much is their 1989 retrospective, and state that it was for marketing purposes.

Apparently CPM implementation in the 1940s was not computer-based. It was manual and centered on what we now know as Activity-on-Arrow or Arrow Diagramming methods. It would be nice to have physical records of these early CPM schedules, but Thayer was not able to discover any in DuPont's or Hanford's archives while writing his book.

Timeline of CPM & PERT Development II
Not only the Navy, but the Army Corps of Engineers. One Col. 'C E Stasik' as a more junior officer in the early 1950's is supposed to have written a monograph on the subject prior to his tenure as an instructor at the Army War College in the 50's and 60's but I am not certain of the precise relation either to earlier work that DuPont did, or to concurrent or later developments. — Preceding unsigned comment added by 50.35.46.178 (talk) 01:13, 17 August 2022 (UTC)

Tnanoc (talk) 17:58, 26 July 2010 (UTC)

Crash Duration Merger
Sorry if any mistakes in the merging process, but the WP merge process is really, really cruddy. Please feel free to fix up. --Hobbes Goodyear (talk) 04:18, 15 November 2011 (UTC)

Did there used to be a nice graphic, and a block of text related to it: the whole thing addressed some aspects of this subject in terms of an airplane coming in, unloading passenger, unloading luggauge, taking on fuel, yadda; and other factors, but it was really good in that it was accessible to a layperson. All you experts really talk amongst yourselves a LOT and mostly FAIL to explain. The editors at the old~fashioned encyclopedias had 1ne thing going for them: they had the authority to say : "keep coming back until you have written something that teaches." — Preceding unsigned comment added by 24.86.18.115 (talk) 06:53, 7 May 2013 (UTC)

Articles for Creation draft
There is a draft that may be worth merging, Wikipedia talk:Articles for creation/Critical Path Analysis. &mdash; rybec   21:23, 1 February 2014 (UTC)

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