Re: Planner-list predecessors for fixed date tasks

[Kurt Maute <kurt maute us>]

On Wed, 2009-10-28 at 23:08 +0100, Ricardo Fernandez wrote:
> Hello Pete,
> 
> I'm not sure to understand, but my comment could help.
> 
> if you have a "Deadline" task  for a part of your project (including,
> for exemple, task A)
>  - you can set "Deadline" task as a fixed date milestone
>  - of course you can't set any predecessor for this fixed date task
>  - so you can't set A as predecessor (for example "end to start" link)
> for "Deadline" task, but...
>  - you can set "Deadline" task as predecessor (same example ; "start
> to end" link) of A
> 
Correct.  The way to set up this relationship is to edit your task A and
set up the deadline as a predecessor with a 'SF' relationship.  Task A
will then be scheduled so that it ends just prior to the deadline task.

> limits for this example :
>  - even if A is an "as soon as possible" task, it will be scheduled to
> "the last moment" before "Deadline". why ? we just wan't it to become
> a "not after" task.

ASAP just means that the task start date will float based on predecessor
relationships.  Planner schedules all tasks (without assigned resources)
assuming that a single resource will work at 100% capacity for the
duration, and sets the start and end dates accordingly.  If you want to
change the start date on a task with a 'SF' relationship, you should
assign a resource and adjust the resource units to something less than
100%.

>  - you can't anticipate A setting it to fixed date (today for
> example). why ?

see above

>  - you can't set any other predecessor to A (a current task ending
> tomorrow, linked "end to start", for example), even if A has been
> scheduled on next year. why ?
> 
Well, if you've set the finish date for task A with a SF or FF
relationship, then we need to let the start date float in order for the
scheduling algorithm to work.

If you created a task B, you could set task A as a predecessor with a SF
or FF relationship.  In this way, you're essentially scheduling from the
deadline back to the present day.

> I agree that external constraints are decisive in project scheduling
> and that Planner constraints rules are too much restrictive.
> but it's not an easy problem, and coding realy accurate rules could be
> an infinite task.
> 
> so just try to use such links with parsimony 
> 
> Regards,
> Ricardo FERNANDEZ
> 
> 
> 
> ______________________________________________________________________
> De :  Alexandre Franke <alexandre franke gmail com>
> Envoyé :  25/10/2009 13:14:00 +0100
> À :  planner <planner-list gnome org>
> Objet :  Planner-list predecessors for fixed date tasks
> 
> > On Sun, Oct 25, 2009 at 5:42 AM, pete davidson <caitifty gmail com> wrote:
> >   
> > > Hi all
> > >     
> > 
> > Hi,
> > 
> >   
> > > I'm trying to use Planner to manage academic grant applications.  As such,
> > > there's a number of key tasks whose dates are externally set and
> > > non-negotiable (such as the date the grant must be submitted to the funding
> > > agency, or the date a letter of intent is due to the funding agency).  I've
> > > been 'locking' these dates by creating a milestone task (eg "Submit grant")
> > > with a schedule of 'on fixed date' on the required date.
> > > 
> > > The problem I'm having is when I try and link these milestone tasks to the
> > > rest of the tasks in the project by setting a predecessor.  This produces
> > > the error "You cannot add a relationship to a task with a Must Start On
> > > constraint."  I've also tried using a one-day task instead of a milestone
> > > task, but get the same error.
> > >     
> > 
> > The problem here is with the meaning of the predecessor relationship.
> > If you set A as a predecessor of B, it means that you cannot start
> > working on B until A is done. So what would happen if you start A on
> > oct 26th, need 4 days to finish it and set B on oct 28th (fixed date)?
> > That wouldn't make any sense because you'd need to work on B but you
> > couldn't since A isn't done yet.
> > 
> > This has nothing to do with the fact that it's a milestone.
> > 
> >   
> > > Is there another approach to dealing with externally set fixed dates that
> > > I'm missing, or a way to set milestone tasks which allows linking to other
> > > tasks?
> > >     
> > 
> > You can do it without the predecessor relationship, I think it's the
> > way that would make the most sense.
> > 
> >   
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