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SS+Lag plus FF+Lag

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Sophia Gerami
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I think we cannot have an activity with 2 relationships with the same successor activity(we need to decide the best logic) but my supervisor says we can have both SS+lag and FF+lag for one successor ! How can it be possible? it should be either SS+lag or FF+lag with the same successor. Do you agree or I'm wrong?

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Zoltan Palffy
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this is known as a compound relationship and is common.

if you only use a SS this could happen

7515
compound.jpg

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Rafael Davila
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Rafael Davila
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The risks of splitting activities that shall be executed continuously can be far more dangerous than pretending concurrent logic does not exists. This is specially true if your model is to apply resource constraints, it might spread apart the segments of an activity that shall be continuous. In such case use of SS(+lag) in combination to FF(+lag) relationships will make a better model.

Best Regards, Rafael

Santosh Bhat
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Sophia, this is a common technique to schedule activities that might happen in parallel, but where the second activitiy is delayed. 

Think for example if yoare digging a long trench, do you wait for the entire trench to be finished, before you start laying pipe? or can you start laying a pipe say once the trench has moved along by a distance? and in the same way, you cannot finish laying the pipe until some time after the trenching is completed.  so a SS/FF link to the same successory reflects this.

It might not pass the DCMA checklist, but in my opinion, that should not be a factor in determing whats realistic.