If an activity is in progress and the progress differs from expected SS relationship shall be updated until the lag is exhausted (required volume was done).
you did not specify the software that you use but I expect that it does not permit to enter and manage volume lags.
So you shall use time lags for SS and FF dependencies.
In your case link Excavation with Gravel bedding using two links: one is SS with 4 days lag and the second is FF with 4 days lag.
Time lag means that certain amount (volume) of work shall be finished before next activity start and planned duration of this volume execution is 4 days.
Check and adjust your lags manually if excavation will be executed faster or slower than expected.
I am sorry, I am not following. It is hard for me to determine SS, SF, and FF usage. I only have basic knowledge, thus, can you explain more. Which should I use then?
Hi, Vladimir. You're right, of course, Spider's ability to designate volume lag is useful here.
In my experience, when users are working with software that has only "generic" lag:
1. SS lags almost always model volume lags.
2. FF lags almost always model time lags.
The distinction is relevant for computing drag, where the drag of work modeled in a volume lag is really work that is captured in the predecessor activity. If it's on the CP with 5D of drag, the project may be shortened by 3D by getting the first 100 metres of trench dug in 2d, thus effectively reducing the volume lag to SS+2D.
With a time lag of 5D, it is the lag itself and not the work in the predecessor that has the drag.
Fraternally in project management,
Steve the Bajan
Member for
24 years 9 months
Member for24 years9 months
Submitted by Vladimir Liberzon on Wed, 2020-02-12 15:46
Lag Volume is an amount of excavation in pnysical units (cubic meters) that must be done before gravel can begin.
Setting time lag one cannot be sure that required amount will be done in exactly 4 days. For some reasons the planned work may be done slower or faster than expected.
Member for
20 years 7 months
Member for20 years7 months
Submitted by Stephen Devaux on Wed, 2020-02-12 15:34
1. physically and sequentially the gravel bedding must start AFTER the excavation. It does not have to wait until ALL of the excavation is done to start the gravel but the excavation must be far enough along as not to impede the progress of the gravel.
so logically this will be a start to start realtionship with a lag meaning the start of the gravel will lag behind the start of the excavation.
2. now we have to consider how much to LAG the gravel behind the excavation. In your example based on time the excavation starts on Jan 1 and the gravel starts on Jan 5 the lag would be a start to start with a 5 day lag.
meaning 5 days after the excavation has started then the gravel can begin.
Member for
24 years 9 monthsIf an activity is in progress
If an activity is in progress and the progress differs from expected SS relationship shall be updated until the lag is exhausted (required volume was done).
Member for
5 years 9 monthsMr. Vlad, Now I understand.
Mr. Vlad,
Now I understand. Thank you!
When the task is now on progress, the SS relationship now becomes driving as well? And should I update relationships each time I update the schedule?
Thank you again!
Member for
24 years 9 monthsYes Russ,you shall apply both
Yes Russ,
you shall apply both dependencieas.
Gravel bedding can start only after certain volume of excavation was done AND can finish only after Excavation was finished.
Member for
5 years 9 monthsPlease correct me Mr. Vlad.
Please correct me Mr. Vlad. Are you saying that when applying an SS, I should apply an FF on that activity as well?
Thank you!
Member for
20 years 7 months"we define FF volume lag as
"we define FF volume lag as the minimal volume of work that shall remain on succeeding activity when preceding activity will finish."
I like that definition for FF lags.
Member for
16 years 3 monthsyes Stephen 4 not 5 fuzzy
yes Stephen 4 not 5 fuzzy math
NO RUSS you do not change lags why would you the relationship and the overlap has not changed
Member for
24 years 9 monthsHi Russ,you did not specify
Hi Russ,
you did not specify the software that you use but I expect that it does not permit to enter and manage volume lags.
So you shall use time lags for SS and FF dependencies.
In your case link Excavation with Gravel bedding using two links: one is SS with 4 days lag and the second is FF with 4 days lag.
Time lag means that certain amount (volume) of work shall be finished before next activity start and planned duration of this volume execution is 4 days.
Check and adjust your lags manually if excavation will be executed faster or slower than expected.
Member for
5 years 9 monthsMr. Stephen and Mr.
Mr. Stephen and Mr. Vladimir,
I am sorry, I am not following. It is hard for me to determine SS, SF, and FF usage. I only have basic knowledge, thus, can you explain more. Which should I use then?
Member for
5 years 9 monthsMr. Zoltan, Does this mean
Mr. Zoltan,
Does this mean that when I change the schedule, I will also manually change lags?
Member for
24 years 9 monthsSteve,we define FF volume lag
Steve,
we define FF volume lag as the minimal volume of work that shall remain on succeeding activity when preceding activity will finish.
Member for
20 years 7 monthsHi, Vladimir. You're right,
Hi, Vladimir. You're right, of course, Spider's ability to designate volume lag is useful here.
In my experience, when users are working with software that has only "generic" lag:
1. SS lags almost always model volume lags.
2. FF lags almost always model time lags.
The distinction is relevant for computing drag, where the drag of work modeled in a volume lag is really work that is captured in the predecessor activity. If it's on the CP with 5D of drag, the project may be shortened by 3D by getting the first 100 metres of trench dug in 2d, thus effectively reducing the volume lag to SS+2D.
With a time lag of 5D, it is the lag itself and not the work in the predecessor that has the drag.
Fraternally in project management,
Steve the Bajan
Member for
24 years 9 monthsIn this case it is right to
In this case it is right to use volume lag.
Lag Volume is an amount of excavation in pnysical units (cubic meters) that must be done before gravel can begin.
Setting time lag one cannot be sure that required amount will be done in exactly 4 days. For some reasons the planned work may be done slower or faster than expected.
Member for
20 years 7 monthsGood explanation, Zoltan. But
Good explanation, Zoltan. But 4 days lag between start-of Jan 1 and start-of Jan 5.
Member for
16 years 3 months2 thigs here 1. physically
2 thigs here
1. physically and sequentially the gravel bedding must start AFTER the excavation. It does not have to wait until ALL of the excavation is done to start the gravel but the excavation must be far enough along as not to impede the progress of the gravel.
so logically this will be a start to start realtionship with a lag meaning the start of the gravel will lag behind the start of the excavation.
2. now we have to consider how much to LAG the gravel behind the excavation. In your example based on time the excavation starts on Jan 1 and the gravel starts on Jan 5 the lag would be a start to start with a 5 day lag.
meaning 5 days after the excavation has started then the gravel can begin.
this is how overlapping is done.