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The Logic Diagramming Method (LDM) – A synopsis

ADM (Arrow Diagramming Method) and PDM (Precedence Diagramming Method) are well established in CPM practice.  ADM denotes activities as arrows between start and finish nodes and connects dependent activities at their nodes, which allows only finish-to-start (FS) logic.  PDM places activities on boxes and uses links to connect the finish or start of an activity to the start or finish of a successor, which allows four types of dependencies.  LDM is a new method of constructing project networks that modifies and extends ADM to permit the four types of PDM logic.  In LDM, activities are time-scaled, ADM-like lines, which obviates the need for activity arrowheads [3].

GPM Sample Schedule Using LDM Notation

As illustrated in the above example, LDM activity notation resembles ADM notation, albeit on a time scale.  Logic ties have multiple arrowheads.  Start-to-start (SS), finish-to-finish (FF) and start-to-finish (SF) logic is accepted through embedded nodes, intermediate of, or right on, activity start and finish nodes.  Driving relationships are conveyed by a common node (FS only) or, owing to the time scale, a vertical link.  Non-controlling links include a horizontal segment or leg, which denotes the gap (calculating the amount of leeway existing) in the relationship.

© 2009 CMAA3

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