Dependencies and Subtasks

Eid E. Eid

Dear All,

Hope you are all safe and in good health.

Can anyone tell me where I can find some good explanation about how dependencies work with tasks/subtasks?

Whenever there is a main task with say 3 sub-tasks, I can see that we can set dependency for the entire main task, in addition to dependencies on the individual subtasks.

However some testing showed that this does not really work as expected.

I have a task A, that has subtasks A1,A2,A3, and another task B.

If I want task A to start 6w before task B starts, I would put in the predecessors of the maint task A : BSS-6w and it works.

However, if I want task A to finish 2w before task B starts, I thought it was logicial to put as a oredecessor to task A : BSF-2w... However it does not work... it does something, but I cant even find the logic of what I am getting. Task A is moved but not where I expected it to be moved, i.e it does not end 2w before task B starts...

I hope my example did not mix up the issue rather than clarifying it...

Can anyone help?

Genevieve P.

Hi @Eid E. Eid

I was able to duplicate this behaviour, but when I removed out the predecessors from rows 8 and 9 (7 and 8), Task C shifts to end one week before Task B, as expected.

To make sure that Task C finishes 1 week before Task B, work from the last task backwards:

Put the 5SF -1w rule as a Predecessor for Subtask C3, instead.

The Subtask C2 should be 9SF -1d

and Subtask C1 should be 8SF -1d

The parent Task C row is the rollup of these dates, so now it will reflect the start date of C1 and end date of C3 (the end date of C3 is the one dependent on Task B, therefore Task C is now dependent on Task B).

You can read more about Dependencies in our Help Center (see here).

Let me know if this works for you!

-Genevieve

Paul Newcome

Have you looked into lag/lead time? It should work if you set Task B's predecessor as Task A and then add in 2 weeks of lead/lag time (I can never remember which is which).

Eid E. Eid

Yes , this is what i meant when i wrote "-2w" and "-6w"

2weeks and 6weeks of lead/lag time

Eid E. Eid

TO clarify more, here is a screenshot of an example that i worked out...

I want task A to start 5w before task B starts- Success

I want task C to finish 1w before task B starts- Cannot do it- See what is get in below....

Paul Newcome

Why not set Task B's predecessor as Task C?

6FS +1w

Eid E. Eid

Because dates of task B could vary because of external parameters, and when i change dates of B, I want everything else to follow.

Paul Newcome

Ah. Got it. Ok. Hmm.............

@Andrée Starå is more well versed than I am with dependencies. Maybe he has some ideas.

Eid E. Eid

Can anyone help on this guys>

Thanks...

Genevieve P.

Hi @Eid E. Eid

I was able to duplicate this behaviour, but when I removed out the predecessors from rows 8 and 9 (7 and 8), Task C shifts to end one week before Task B, as expected.

To make sure that Task C finishes 1 week before Task B, work from the last task backwards:

Put the 5SF -1w rule as a Predecessor for Subtask C3, instead.

The Subtask C2 should be 9SF -1d

and Subtask C1 should be 8SF -1d

The parent Task C row is the rollup of these dates, so now it will reflect the start date of C1 and end date of C3 (the end date of C3 is the one dependent on Task B, therefore Task C is now dependent on Task B).

You can read more about Dependencies in our Help Center (see here).

Let me know if this works for you!

-Genevieve

Eid E. Eid

Thanks a lot...

It is clear now... Although I cannot do what i wanted to do. At least I know it cannot be done..

Thanks a lot for your help.

This is a great comunity

Genevieve P.

Happy to help! And glad you like the Community.

But can I ask what didn't work as expected? Is the end result when detailing the predecessors in the Child tasks different than what you wanted?

Eid E. Eid

Sure,

I want to keep the relationships in the subtasks in the "forward" order, not backwards, while making sure that the whole group finishes at a given date.

During project planning, putting the tasks in backward as u suggest would do the job,

However if during execution, the first task is done 3 weeks before it was supposed to, then all the dependancies have to be broken...

Genevieve P.

Oh I see! In that case Paul's suggestion of having Task B dependent on Task C would be the way to have the subtasks move "forward". Hmm this is a tricky one.

@Andrée Starå I would also be interested to know if you have any ideas here.