I usually avoid sessions at technical conferences titled “Great Debates” as many are prone to having the important issues discussed overridden by the histrionics of the participants.

While entertaining, the “meat” of the session often is lost. However, I would enjoy readers’ input for a debate topic raised at a professional standards meeting I attended last week, that being the benefits of use of a summary or full logic network to calculate schedule risk.


Some of the benefits of use of the full network include that:

·    the work is already done – why not use it? – why not save the cost of making a summary?

·      in making a summary, some less obvious paths may be missed

·      much of the risk is caused by the merging paths of near critical paths, this “risk” then being lost in any summary.


Some of the benefits of preparation and use of a summary network include that:

·      the effort to review and correct errors and omissions of the full network may be more time consuming and fraught with controversy than preparation of a summary network

·    presentation of a summary and resulting calculation of risk analysis are certainly more “readable” to intended upper management audiences

·      much of the risk, say of a fragnet of fifty activities of one subcontractor, may be lost as some durations are modeled high and others low, unless additional care is taken to properly account for correlation between activities.


The most important point in both arguments is that calculation for schedule risk differs fundamentally from that of cost risk. The sum of a great number of costs of activities plus or minus some degree of uncertainly will tend towards the simple sum of unadjusted costs.

The same is not true for durations of activities in a logic network and will always trend to be significantly higher than that simple forward pass calculation.


(This is more fully discussed on one of our prior blog posts, ”You Can’t Always Get What You Want ...” PROBABILITY OF COMPLETION ON TIME, posted 9/17/2009.)

My comments on the topic are that there may be enough significant opportunity to either overstate or understate risk utilizing either method, and suggest that perhaps the professional should utilize both methods of analysis, compare for mutual support (bringing better endorsement) or divergence (calling for yet more review and analysis). 

While more expensive, the whole purpose of the exercise is to bring better understanding of the issues, and thus should be done right or not at all.

I would look forward to comments to this blog, or to more fully developed papers and presentations at one of our technical society journals or conferences.

The Construction CPM Conference

Upcoming conferences (which I attend) include:

·      your Construction CPM Conference, January 27-30, 2013, New Orleans

·      PMI Scheduling Community’s 11th Annual Conference, May 2013, Baltimore


·      AACEi’s 57th Annual Conference, June 30 – July 3, 2013, Washington DC


The deadline for $825 early bird pricing at your Construction CPM Conference, January 27-30, 2013, New Orleans is October 15th. Being sandwiched between the entertainment of the first week of Mardi Gras and Super Bowl, we expect a fun time as well as 100 technical sessions on a variety of topics and software products utilized in the scheduling profession. Additional ideas from you on improving this event are welcome.