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Defination of Lag, Float & Negative Float

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Irfan Khan
User offline. Last seen 2 weeks 3 days ago. Offline
Joined: 19 Jul 2009
Posts: 123
I need understandable definition of following :

1.Lag
2.Float
3.Negative Float

with best regards


IRFAN KHAN

Replies

Rafael Davila
User offline. Last seen 21 hours 30 min ago. Offline
Joined: 1 Mar 2004
Posts: 3585
CPM is about relationships otherwise is a Bar Chart.

Some old software started to bring welcomed PDM functionality to better model real life situation but never were updated to better deal with relationships. lag calendars, lag filters, longest path value (as per Ron Winter) and better ways to report on the relationships are among the many features left out.

Spider Project is alive while others are either dead or going backwards.

Best regards,
Rafael
Hi Rafael,
in Spider Project you can create or select special calendar for any Time Lag.
So separate calendars can be created and assigned to activities, resources and lags.
But in Spider Project you can also define Volume Lags that I consider as much more interesting and useful.
An example: you can start to lower pipes when the distance to ditching crew will achieve 500 meters.
Best Regards,
Vladimir
Rafael Davila
User offline. Last seen 21 hours 30 min ago. Offline
Joined: 1 Mar 2004
Posts: 3585
Thanks again, and indeed THE REAL LIFE IS NOT THAT SIMPLE.

I got the information from a forum post and yes I misunderstood it as to mean any. I dont’t have P6, good to know although you already must know I dont’t like P6, we gave it a try for a few weeks before discarding it. Let’s see what happens when many medium sized contractors and government agencies start to deal with such aberration.

What about Spider Project, do it has the option?

Best regards,
Rafael
Hi Rafael,
unfortunately P6 does not permit to set the individual calendars to relationship lags. It only suggests to select one of four options (predecessor, successor, 24 hours or default calendar) for ALL relationships lags. The real life is not that simple.
Besides time lags we often use volume lags but not in P3/P6.
Regards,
Vladimir
Rafael Davila
User offline. Last seen 21 hours 30 min ago. Offline
Joined: 1 Mar 2004
Posts: 3585
Thanks Vladimir

Appropriate call.

To the concepts of float and lag I would like to add that both are computed upon calendars.

Different software use different calendars for lag; some use successor activity while others use predecessor, and a few like P6 let you assign an individual calendar to your relationship lags.

Float is based on the activity calendar so different activities with different calendars will show float based on different calendars.

Cordially,
Rafael
Rafael,
you have made an error. The correct definition:

Total Float can be defined either as:
a.The difference between early start and late start.
b.The difference between the early finish and late finish.
c.The smaller of the two.

Regards,
Vladimir
Rafael Davila
User offline. Last seen 21 hours 30 min ago. Offline
Joined: 1 Mar 2004
Posts: 3585
Lag is the number of time units from the start to finish of a relationship, a lag can either be positive or negative. If the relationship is not driving then it has no impact on the successor dates unless latter on it becomes a driving relationship. Think of lag as the duration of a particular relationship that might or may not be driving.

In P3 float can be defined either as:
a.The difference between early start and early finish.
b.The difference between the late start and late finish.
c.The smaller of the two.
Note that a. and b. are not necessarily equal when allowing splitting or after progress is applied.

When you impose a constraints or a project finish date the backward computations for late dates are redefined to be from this constraint date rather than from the last activity dates on the path, because the constraint date can be before the activity early dates float can be found to be negative along the particular path.

You can set open path to be critical or not as to fix the open path backward computations to start either from the dates of last activity on the open path or from the dates of the last activity on the net. This is a special type of finish constraint that will also affect your computations of float; this is applied at the network level instead of at a particular activity.

Sorry these are more complicated definitions but eventually you will have to cope with them.

Best regards,
Rafael
Charito monserrat...
User offline. Last seen 4 years 27 weeks ago. Offline
Joined: 18 Jan 2009
Posts: 7

good day...following are the definition of...

1. Lag_ means is the number of time units from the start or finish of an activity to the start or finish of its successor. a lag can either be positive or negative.

2. Positive Float_represents the number of workperiod an activity can slip before it possibly affects the project finish.

3. Negative Float_program calculates a negative float only when you impose a constraints or a project finish date. the late dates are earlier than the early dates, which indicates that the activity is behind schedule.

hope you got a brighter ida of the meaning behind the terms... good day...

regards,

rica....email:cheplan88@gmail.com