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Negative Slack with SF dependancy

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Level 3
Does Workfront support negative lags in SF dependencies? One of my PMs has a project go-live date (that is already defined) and a task to be completed one week prior to the go-live. He's attempting to use a Start to Finish dependency and include the 5 days using '4sf-5d'. When we do this, we get an error: "Please change your lag times to positive numbers". We can successfully apply negative lags in all other types of dependencies (FS,FF,SS), but not SF. Thoughts? Thank you! Jodi Biscevic GM Financial - International Operations
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Level 10
I can't say I've ever used the SF option. I've used all the others though. I normally use the default of FS, or in your scenario I would use SS-5d. Or if you want it to start 5 days from the end of the go-live task I would use FF-5d. Either one should get you what you're looking for.

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Level 2
I'm having the same issue with not being able to have an SF dependency with a negative lag. I don't understand why this dependency can't have a negative lag time. My use case is that I have anchor tasks for an event. I have tasks that happen before the event and tasks that happen after the event. I need the pre-event tasks to have an SF dependency so that the Pre-Event task is finished before the start of the Event (anchor task). This would allow me to adjust the duration of the task to adjust the start date of the pre-event task. Right now, the only option I have is to use an FS with a negative lag time. But this causes me and others to now adjust the lag time and duration to make the start and due date of the pre-event task work. Do we know if Workfront is working on having this feature? I know MS Project and many other work management suites have this capability. Brian Sapp Esri

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Level 3
SF is always a rare and exciting predecessor type to use in a project. For the original topic in the list, the task cannot finish until the predecessor starts. Therefore, Lag is considered overlap going forward and not backward (since you are backward passing the logic). If the "preparation work" is required prior to go-live, then no lag with whatever duration the work requires will provide the correct behavior (as you stated your desires). Negative lag goes against the "task cannot finish" logic (the true letter of intent) so I can see why Workfront prohibits the negative lag. To the thread immediately above, sequencing multiple events from an anchor point in the middle will not calculate a critical path, since everything on the path hinges from a fixed date in the middle of the project. Any "predecessors" are actually successors and therefore would not move the date. Instead, performing a forward pass of the schedule with a start no earlier than constraint (or finish no later than) on the event in the middle will show you compression to the timeline with float leading up to the event. Now, what is hard to see from the "middle" is if anything required for the event can impact anything subsequent to it. You would have to tie the predecessors in the subsequent tasks to the pre-event tasks as well as the event to show the impact to the overall project. This is one of those situations when it depends on what you are trying to have your model tell you. What dates are OK to miss: the tasks leading up to the event, the event in the middle, or the tasks after the event? When tasks are getting missed, where is the compression? Finding tasks in the middle, without a milestone view or custom field/report is hard to do since projects are really focused on a goal (end or beginning of a project in total). Just my $0.02. Dale Whitchurch Arthrex Inc