Some insights on PDM, ADM and Schedule

这篇文章比较了PDM(Precedence Diagramming Method)与ADM(Arrow Diagramming Method)的不同， 并认为PDM是最适于进行CPM(Critical Path Method) Schedule的. 文章中有几个观点很好:

1. A PDM schedule is simply a bar chart with connecting lines and arrows that shows which bars are tied to other bars, logically. Briefly explained, if you can draw a bar chart, then you can draft a PDM schedule, probably on the computer.

2. Budgets and accounting systems that compare planned expenses and revenue to actual expenses and revenue are an effective way of monitoring results—after the facts and events have already occurred.

Schedules (defined as planned performance sequences) are an excellent way of measuring future results.

Schedule不但可以用来预测未来的结果，而且还是一种法律证据：

But more than that, the prebid or preconstruction PDM schedule is proof-positive of precisely what is planned and intended by the contractor when a project is bid or before it starts.

Later, when unforeseen delays, interferences, shutdowns, change orders, work sequence changes, and a host of other noncontractor-caused problems are encountered, the effects of those unplanned, unforeseen events can be readily noted by adding them to the PDM schedule as they occur. An after-the-fact, actually performed schedule is called an as-built schedule.

As-built schedules, when compared to as-bid or as-planned schedules, provide what attorneys refer to as entitlement arguments, documented proof for the payment of monetary damages. Without any as-bid, as-planned, and as-built schedules, there are no entitlement proofs and, thus, there can be no damages due the contractor for hours, days, weeks, months, and even years wasted on what was perceived to be a clean, money-making project until all the problems began.

Schedules are not the only way to prove entitlements for damages, but they are miles ahead of whatever is in second place.