Start-to-Finish

[scott_hanebutt]

I have been experimenting with the start-to-finish relationship and am
confused about the way it works. I understand the concept of when to use
this relationship. My problem is the way it acts.

The name implies that predecessor must start before the succesor can end.
It says nothing against the possibility that the predeccesor might finish
before the successor finishes.

I set up a simple trial of this relationship and got unexected results. I
did the following.

TasK1 duration 2 days start date is project start date
Task2 duration 3 days start date is project start date

I then added a start to finish relationship to task 2. At this point
project moved task2's start and finish date before the project start date so
that task 2 ended on the same day that Task1 started.

The way I see it the dates should not have changed. Task1 was already
starting before task2 was finishing.

I am missing something?

Thanks,
Scott Hanebutt

 

[davegb]

I have been experimenting with the start-to-finish relationship and am
confused about the way it works. I understand the concept of when to use
this relationship. My problem is the way it acts.

The name implies that predecessor must start before the succesor can end.
It says nothing against the possibility that the predeccesor might finish
before the successor finishes.

I set up a simple trial of this relationship and got unexected results. I
did the following.

TasK1 duration 2 days start date is project start date
Task2 duration 3 days start date is project start date

I then added a start to finish relationship to task 2. At this point
project moved task2's start and finish date before the project start date so
that task 2 ended on the same day that Task1 started.

The way I see it the dates should not have changed. Task1 was already
starting before task2 was finishing.

I am missing something?

Thanks,
Scott Hanebutt

You're interpretation of start/finish is incorrect. SF relationships
mean the the successor task finishes when the predecessor starts. It
basically amounts to scheduling backwards. As in all relationships, the
predeccessor drives the successor. A common example might be:
I have to fix both the radio and the brakes on my car. I have to leave
to go somewhere in the car at 5pm. I estimate it will take 2 hrs to do
the brakes, so I have to start them no later than 3pm. If I estimate
the radio will take 1hr, I have to start it by 2pm. The start of fixing
the brakes is determining the finish of fixing the radio.
In your example, the software is pushing task2 to finish when task one
starts, as it should.
Hope this helps in your world.

 

[Steve House [Project MVP]]

Adding to Dave's comment ... remember that in addition to the SF link
driving the timing of the successor there's also the constraint to finish
the task as soon as possible after the project start. The start of the
predecessor determines the earliest possible time the successor can finish
and the ASAP constraint prevents it from finishing later unless something
else such as a lag time gets into the picture.