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    Can anybody explain to me, where you put dummy arcs, I can never seem to get them right!

    Thanks,
    Klaxoii


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    yeahhh
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    (Original post by Klaxoii)
    Can anybody explain to me, where you put dummy arcs, I can never seem to get them right!

    Thanks,
    Klaxoii


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    Dummy events are used to preserve precedence. Also, the activity defined by (i, j) (where i is the start event, j is the end event) must be unique, there can be no ambiguity to this.
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    You use them when one activity is followed by another activity, but you have another activity that follows both the original activity and a different activity. So, say C follows A, but D follows both B and A.

    The first diagram says that D follows A and B, which is right, but it also says that C follows both A and B, which is wrong. The second diagram shows that C follows A only, but D follows both B and C.
    Also, if two arcs directly join the same nodes, a dummy activity has to be used, for reasons I don't quite understand.
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    (Original post by Juzey)
    Also, if two arcs directly join the same nodes, a dummy activity has to be used, for reasons I don't quite understand.
    This is why

    (Original post by lizard54142)
    The activity defined by (i, j) (where i is the start event, j is the end event) must be unique, there can be no ambiguity to this.
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    (Original post by Juzey)
    You use them when one activity is followed by another activity, but you have another activity that follows both the original activity and a different activity. So, say C follows A, but D follows both B and A.

    The first diagram says that D follows A and B, which is right, but it also says that C follows both A and B, which is wrong. The second diagram shows that C follows A only, but D follows both B and C.
    Also, if two arcs directly join the same nodes, a dummy activity has to be used, for reasons I don't quite understand.
    Thanks for the feedback guys, a bit more practice and I should be okay with critical paths


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