Precedence Relationships in ALICE

The dependencies between activities in a schedule are defined by precedence relationships. 
ALICE supports the 4 standard precedence types most commonly used in scheduling software: FS, SS, FF, and SF.

In addition, ALICE supports more strict precedence definitions that allow users an increased degree of control in defining dependencies. We call these ALICE custom precedence types. Read on to learn more.

 

Standard Precedence Types

The most common types of dependencies are the following four (4):

1. Finish-To-Start (FS): Activity B can begin after A is finished.

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In other words: Finish A ≤ Start B

 

2. Start-To-Start (SS): Activity B can start at the same time as A.

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In other words: Start A ≤ Start B

 

3. Finish-To-Finish (FF): Activity B can finish at the same time as A.

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In other words: Finish A ≤ Finish B

 

4. Start-To-Finish (SF): Activity B can finish at the same time as A starts.

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In other words: Start A ≤ Finish B

 

ALICE Custom Precedence Types

In ALICE, the above relationship types are extended by adding the "At" type, which imposes the type of dependency. Therefore, the additional precedency types are transformed to:

1. Finish - At - Start (FaS): Activity B must begin after A is finished.

Or: Finish A = Start B

2. Start - At - Start (SaS): Activity B must start at the same time as A.

Or: Start A = Start B

3. Finish - At - Finish (FaF): Activity B must finish at the same time as A finishes.

Or: Finish A = Finish B

4. Start - At - Finish (SaF): Activity B must finish at the same time as A starts.

Or: Start A = Finish B

Be mindful when using the custom precedence types, as they impose a very strict relationship between activities, which can render your schedule infeasible. 

 

 

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