Dependency (project management)
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In a project network, a dependency is a link amongst a project's terminal elements.
There are four kinds of dependencies with respect to ordering terminal elements (in order of decreasing frequency of use):
- Finish to start (FS)
- A FS B = B doesn't start before A is finished
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- (Foundations dug) FS (Concrete poured)
- Finish to finish (FF)
- A FF B = B doesn't finish before A is finished
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- (Entire book written) FF (Last chapter written)
- Start to finish (SF)
- A SF B = B doesn't finish before A starts
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- (New shift started) SF (Previous shift finished)
- Start to start (SS).
- A SS B = B doesn't start before A starts
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Dependency-SS.png
image:Dependency-SS.png
- (Project work started) SS (Project management activities started)
There are three kinds of dependencies with respect to the reason for the existence of dependency:
- Causal (logical)
- It is impossible to edit a text before it is written
- It is illogical to pour concrete before you dig the foundations
- Resource constraints
- It is logically possible to paint four walls in a room simultaneously but there is only one painter
- Discretionary
- I want to paint the living room before painting the dining room, although I could do it the other way round, too
Traditional critical path-derived schedules are based only on causal (logical) dependencies. The critical chain method necessitates taking into account resource constraint-derived dependencies as well.