#287 Dates types and critical path


This is an extension of
[ 1267746 ] Planned versus Actual dates


As it is common in all planning method (PERT, CPM,
etc...) different types of dates are defined and
useful. As there are many mistakes in understanding
this type of dates (the most known : latest and
earliest) many planning organisations (in companies)
users have defined other types that are enduser more
useful and not misunderstanding sources.

The free way and/or free end date :

it is the end date (or duration) after the task which
doesn't change any other date into the planning. The
meaning is simple you can end the work till this date
'theorically - following the model, and remining that
it forget always some constraints) without changing
anything. The rules is generally ask to the project
manager about the reality of this possibility

The latest :

The common latest date, after this end date of a task
if anybody who works after can't many is work into the
estimated time and the other no shortly the project end
will be late. This date is generally not communicated
to anybody else than the planning because of risk of
misunderstanding by other which don't integrated all

The scheduled dates :

They the beging and end scheduled by planning with
project manager agreement which respect the full
constraints. These are the dates published.

The earliest :

The absolute earliest (taking in account only the
external "not before dates". They are again a planning
tools which require interpretation, they are "not
enduser" dates.
But the relative earliest is the ealiest begin date
which are consequences of the sheduled dates of
precedent tasks.

The external constraint dates :

They can be for task ot milestones : not before or not
later than. Generally not earlier applies to begin and
not later to the end.

The critical(s) path(s) :

The "absolute" crtical path is again with a limited
interest to the planning job.
But to find all the task which are on ways into the
planning where the total of free ways are less than a
value estimated by the planning are "critical". This is
a major concept.
For example whe have a project which duration is six
month if a way has less than 10 days of free ways are
considered as critical path.

NEED in my opinion

1- limit dates :
- begin not before (is it)
- end not later (lack)
nota : for my own usage, to be clear, for external
constraint, I always ceate milesstones (genrally an
external fact, event, not a task)

2- The calculated "not begin before"

3- The calculated "end free way" no later than

4- A scheduled begin date which can be changed and
fixed after the "not begin before"

5- A scheduled end date which can be changed and fixed
not after the "end free way".
Interactive calculations : The duration is calculated
from the to scheduled dates versus a duration change
calculates the end or begin if end limit passed.

6- Critical path following the concept defined upon

7- Make possibility to show the graphic at early (as
defined) and save state

8- Make possibility to show the graphic at latest (as
defined) and save state

9- show the free way after the task with a graphic
symbol (thin green rectangle for example)

10- show the "free time before" ("taking in account the
scheduled date of other task the task can begin at
earliest date of")

11- Add symbols as -> or <- (anyother) to show the time
constraints on the graphic

I am completely aware that :
1- it is possible not to adopt all my proposals
2- it is not possible to present these proposal
separately because of the full intrisic coherence.

After discussion elements can be separated.


No remarks


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