Other Scheduling Methods - Construction Project Scheduling and Control - page 322

The following additional definitions may be useful in understanding GPM.
• Benchmark: reference network object denoting a fixed start or completion event
(occurs in an instant) that has zero total float and that is used to model an
overarching milestone or contractual deadline
• Embedded node: event intermediate of, or right on, the start or finish node
of an activity, for which the activity is connected to a predecessor or from a
successor activity, milestone, or benchmark
• Link or logic tie: network object drawn as a directed edge connecting the two
activities, and activity and an event (milestone or benchmark), or two events
• Logic diagramming method (LDM): timed-scaled network notation that uses
bars from start-to-finish nodes to represent activities and that links activities
through their start or finish nodes or through embedded nodes. LDM networks
model the four types of PDM logic commonly allowed in CPM networks when
using precedence diagraming method notation
• Network: flow graph of the schedule comprising rule encoded, algorithmic
activities, embedded nodes, milestones, and benchmarks, which are linked by
designated predecessor-successor links
• Planned dates: physically manipulated dates, between early and late dates, that
do not replace early dates and generate drift, thereby preserving total float
• Synchronous: interface that in real time, in response to, and during manipula-
tion by the user of network objects along the timeline, recalculates and refreshes
the display of the schedule in its instant state.
Relationship Diagramming Method (RDM) 9
In 2004, the relationship diagramming method (RDM) was introduced by Dr. Fredric
Plotnick to address issues resulting from ambiguities of logic in software implemen-
tations of the precedence diagramming method (PDM). Engineering News-Record
(ENR) magazine highlighted a number of these issues in a 2003 cover story that
cited Dr. Plotnick, a scheduling and legal expert.
RDM started from a premise that ADM (arrow diagramming method) and PDM
improved upon the Gantt chart by recording (and use for further calculation) some
of the data that the project manager and team considered in preparation of a plan
and schedule. However, the quantity of data that could be stored in early computers
was limited, and, thus, many assumptions relating to the logic were not recorded.
The general solution to the problem was therefore to obtain, record, and then use
information relating to these assumptions.
The RDM format begins by allowing the recording of this additional informa-
tion and then augments the calculations and resultant data output. While the primary
9 This section was mainly written by the idea's developer, Dr. Fredric Plotnick.