Best practice - predecessor tasks

[matthewg156]

Hi there

I have a best practice question regarding tasks and predecessors.

As an example, say I have the following tasks:

1. Buy ingredients
2. Bake cake
3. Eat cake
4. Cake project completed (milestone)

The tasks obviously have each previous one as its predecessor. Now, fo
the last task, the milestone, each of the tasks 1-3 must be complet
before it can be finished. Do I make the predecessor tasks for task 4 a
tasks 1,2,3? Or is it enough to just put task 3 as the predecessor fo
task 4, as task 3 requires task 2 which requires task 1, etc

 

[Mike Glen]

Hi Matthew,

Welcome to this Microsoft Project newsgroup

Don't put in redundant logic links, the Milestone is no different from the
other tasks. Link them all in line.

FAQs, companion products and other useful Project information can be seen at
this web address: http://project.mvps.org/faqs.htm

Hope this helps - please let us know how you get on

Mike Glen
MS Project MVP
See http://tinyurl.com/2xbhc for my free Project Tutorials

 

[Steve House [MVP]]

My old philosophy professor called this the problem of efficient versus
sufficient causes. All of the tasks in a chain leading to a given task are
antecedents to the task in question but the predecessor(s) are tasks that
actually produce delverables needed for the task in question to proceed. In
your task list "Buy Ingredients" is certainly an antecedent but the task
that actually produces the "cake" deliverable needed for "Eat Cake" to start
is the "Bake Cake" task. So "Eat Cake" has one predecessor "Bake Cake"
while "Bake ..." has as its predecessopr "Buy..."

 

[go83]

Can someone expand a little bit on the benefit of each task needing a
predecessor and successor task? I understand the common sense benefits
of using predecessors for a task that can't logically complete before
another task finishes, but let's say 5 out of 10 project tasks can take
place immediately. What's the benefit in Project of tying them to a
"project start" Milestone? What are the risks of not doing so?

Thanks.

 

[Rob Schneider]

Simplistically ... predecesors are tasks that must be complete (to the
degree defined in the logic) before the successor can start.

By making sure all tasks have a predecessor and successor allows you to
build a model of the project which can give you a computed end date,
cost, etc. That's the purpose of Project--to do for you the relatively
complex computations associated with a network model of a Project.

Your example of saying 5 tasks can take place immediately .. which I
guess you mean can happen As Soon As Possible. So, what I would do is
model the project that way. Say (if this is how it the project works for
your project, you would have a tasks to "start" the project (usually a
milestone duration=0). Then the successor to this start task are the 5
tasks which can start ASAP. That doesn't say it is yet "possible", just
"as soon as possible". Project can then tell you what is possible
within the limits of the model definition.. say you have only so many
resources and even though assigned, cannot work on all5 at once. When
you Level in Project, Project will tell you. If you say "but I know we
can do all these five tasks now and I don't need Project to tell me",
well ok. That's fine. Just if you want to have model in Project, then
model it so that there the right logic which allows it indeed for all to
start now.

There is no "risk" of not tying all this to a project "start" milestone
that I can think of. It's just a convenience. Sometimes the project
start is not known and by having all the downstream tasks linked to the
one start, you can adjust that one start and everything else downstream
"flows" into place.


--rms

www.rmschneider.com

 

[John]

Can someone expand a little bit on the benefit of each task needing a
predecessor and successor task? I understand the common sense benefits
of using predecessors for a task that can't logically complete before
another task finishes, but let's say 5 out of 10 project tasks can take
place immediately. What's the benefit in Project of tying them to a
"project start" Milestone? What are the risks of not doing so?

Thanks.

go83,
Rob gave an excellent explanation. Just a couple of thoughts I'd like to
add.

From my perspective every task in a project plan MUST have a successor,
even if that successor is simply the end milestone. If you say, "no,
some of my tasks do not have a successor", then I've got to ask, "why is
the task even in the plan, if it doesn't contribute to at least the end
milestone?"

On the other hand, a very few select tasks may not have a realistic
predecessor. For example, you know ahead of time that a particular
resource (labor or non-labor) will not be available until some point in
time after the project start. In that case you should use a
"start-no-earlier-than" constraint for that task. You could also use a
predecessor from the start milestone with a lag to the date of
availability but if for some reason the start milestone is moved, so
will the task with the delay.

My thoughts.

John
Project MVP

 

[Sai]

Can someone expand a little bit on the benefit of each task needing a
predecessor and successor task?  I understand the common sense benefits
of using predecessors for a task that can't logically complete before
another task finishes, but let's say 5 out of 10 project tasks can take
place immediately.  What's the benefit in Project of tying them to a
"project start" Milestone?  What are the risks of not doing so?

Thanks.

--
go83
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It is not a must that the tasks should be linked to *start
milestones*.

It is a general practice that network should be closed, but you may
have cases that contradicts.

Let me share my thoughts on "why" you should have predecessors and
successors to a task
1. I hope you know "milestones" can be hard or soft. Hard milestones
have constraints, where as soft milestone will have "as-soon-as-
possible" or "as-late-as-possible" contraints. Naturally, every task
will depend on another task event or on external event. These external
events can be treated as hard milestones.
2. Also by default, Project sets the late finish date for tasks
without successors or constraints to be the project finish date. This
means, that task will not be critical task, To override this Choose
Tools | Options | Calculation tab and check "Calculate multiple
critical paths". This ensures, Project sets the late finish date for
these tasks to be their early finish date, making the task critical.

Please let me know if this answers you question.

- Sai, PMP, PMI-SP, MCT, MCTS
http://saipower.wordpress.com

 

[aww91]

Some clarification please. Going back to the original example, ho
would you recommend tying a new task, that does not have a successor, t
the project “end” milestone? For example:

1. Buy ingredients
2. Bake cake
3. Monitor oven temp.
4. Eat cake
5. Cake project completed (milestone)

Thanks in advance for your reply