DEFINITIONS

Earliest Start Time for Node j (ES_j):
Earliest time at which activities coming out of Node j can start (or equivalently, the earliest time by which all activities coming in to Node j can be completed):
 

Latest Completion Time for Node i (LC_i):
Latest time by which activities coming in to Node i must be completed in order that the project be completed in its minimum duration (or equivalently, the latest time by which all activities coming out of Node i must start so that the project's completion is not delayed):
 

EXAMPLE:
Consider the part of a network shown below with activity durations above the arcs. Focus on Node j=4.

ES₄= (=ES_4-5=ES_4-6=ES_4-7) $\geq$ 4 + 4 (=ES₁+D₁₄)
                                                $\geq$ 6 + 3 (=ES₂+D₂₄)
                                                $\geq$ 4 + 6 (=ES₃+D₃₄)
Thus ES₄=Max{8,9,10} = 10
 

Next focus again on Node i=4.
 

LC₄= (=LC_1-4=LC_2-4= LC_3-4) $\leq$ 18 - 3 (=LC₄-D₁₄)
                                                   $\leq$ 17 - 5 (=LC₅-D₁₅)
                                                  $\leq$ 15 - 4 (=LC₆-D₁₆)
Thus LC₄=Min{15,12,11} = 11

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