## Forum Discussion

# Task dependencies

- Sep 09, 2024
The whole purpose of dependencies is to shown interaction of tasks. Normally dependencies show a logical sequence of tasks resulting in a Gantt display that more-less follows a waterfall.

In your examples the first sequence, task 14 dependent on task 13 which is dependent on task 12, shows the correct sequence whereas the second sequence shows task 14 dependent on both task 12 and 13 but task 13's dependency on task 12 is missing. Graphically, the two scenarios look like this:

So when laid out as described in your screen shots, no, the third task in both cases does not start at the same time. If the dependency between the first and second tasks is shown as described verbally, then the two sequences look like this:

The third task in each sequence does start at the same time, but there is a redundant dependency between task d and f in the second sequence. Technically it isn't wrong, but it adds no value and can add confusion, or raise doubt (i.e. why? what are we missing?).

John

Per you item b) it sounds like the sequence of tasks is 12, 13, 14 in waterfall fashion. That is, task 13 starts when task 12 is complete and task 14 starts when task 13 is complete. Therefore, the sequence shown in b) is the correct dependency.

John

- markPMSep 09, 2024Copper Contributor
Thanks John, Just to understand, what is the difference between these approaches? Because in both cases task 14 would start on the same date.

Marcos.- John-projectSep 09, 2024Silver Contributor
The whole purpose of dependencies is to shown interaction of tasks. Normally dependencies show a logical sequence of tasks resulting in a Gantt display that more-less follows a waterfall.

In your examples the first sequence, task 14 dependent on task 13 which is dependent on task 12, shows the correct sequence whereas the second sequence shows task 14 dependent on both task 12 and 13 but task 13's dependency on task 12 is missing. Graphically, the two scenarios look like this:

So when laid out as described in your screen shots, no, the third task in both cases does not start at the same time. If the dependency between the first and second tasks is shown as described verbally, then the two sequences look like this:

The third task in each sequence does start at the same time, but there is a redundant dependency between task d and f in the second sequence. Technically it isn't wrong, but it adds no value and can add confusion, or raise doubt (i.e. why? what are we missing?).

John

- markPMSep 11, 2024Copper ContributorUnderstood! Thanks so much for such an in-depth explanation.