How P3 is handling relationships?

Hi,

If the scheduling logic is to start B 4 days after starting A then it must be B SS A with 4 days positive lag.

If you go for the other, as the project progress, your basic scheduling requirement (starting B after 4 days of A) may not be met.

Regards,

Manu

I think first one is better.

Regards.

I don’t like to use negative lag.

If A has a delay douring the work (10 to 12 duration), it will delay B (using FS with negative lag).

Regards.

Marcio Eduardo
Rio de Janeiro - Brazil.

Surely, it depends on the relationship between the two activities.

If the start of B is dependant upon the progress made on A, then the only credible (IMHO) relationship would be FS with negative lag, as the SS relationship effectively says that 4 days after A has started, B can start, independent of the progress made on A.

Yes, sure.

But in the example, B has to start 4 days after A, and not start 6 days before A finish date (two diferent things).
In may opinion FS with negative lag is wrong in this specific example.

Regards.

Hi All,

If and only if the start of B is dependent upon the start of A then B having A as a predecessor with SS+4days is good enough. Though if B is also dependent upon the producivity/speed/buffer of A then it should be FS or even FF.

To clarify as from where i am comming from,i’ll explain as follows.

When i am saying B is dependent upon the progress/buffer of A, I consider A being the ’Subgrade’ and B being the ’Spreading of Gravel’ in a project of highway construction. B could start after 4 days as there would be enough (buffer) subgrade available though after a few days if the A slows down then B has to automatically match with the speed of A and in this case FF or FS with ’Retained Logic’ would model the situation realistically.

Regards
Rashid Iqbal

Hi,

Does any of the planning softwares has an option for conditional relationships?. For example "IF actual progress of task A is 40% then start task B".

I think such an option will help in situations like this.

Manu.

Microsoft Project allows a SS+50% or a FS-50% relationship.

Paul E Harris
Eastwood Harris Pty Ltd, Melbourne, Australia
Planning and Scheduling Book Publishers, Training & Consulting
www.eh.com.au

I think the most important thing is the length of the first activity. If the first activity has a length of 365 days and something has to happen somewhere at the end, the best solution is a negative lag. Because, if something happens on the way of the first activity a SS relationship can never show the influence on the second activity. So you have to consider case by case. Important is to describe the relationship by your own words - the best description mostly is the best link.

Hannes

Sorry ... but sometimes i think that we complicate simple things.

The question was:
"if two activies A & B of 10 and 15 days. B should start after 4 days of A start.
What is better to logic them?

Should they B SS A with 4 days +ve lag. OR
B FS A with 6 days -ve lag."

MAKE IT SIMPLE - That is the best answer.

thanks deeply for everybody answer

however, my question is after something else.

in fact, it will be very debatable, if we consider the nature of the activity. in this case, every activity has its own answer, ex engg activities will different from construction and from IT ones...... etc.

i am looking specifically for how P3 is handling it. and what is better for P3? or they r equal? specially when progressing....

with my great appreciate for each word of yours.

"Microsoft Project allows a SS+50% or a FS-50% relationship."

Paul,

Could you please tell me how to go to that option in MSP?

Regards,

manu.

Just type in +50% etc in the lag box in the same way as one would type in a lead or lag of say +5d or -5d.

Paul E Harris
Eastwood Harris Pty Ltd, Melbourne, Australia
Planning and Scheduling Book Publishers, Training & Consulting
www.eh.com.au

Thank you,

It worked.

Manu.

MSP ???? i think this is about P3
let me rewrite my question
.
.
thanks deeply for everybody answer

however, my question is after something else.

in fact, it will be very debatable, if we consider the nature of the activity. in this case, every activity has its own answer, ex engg activities will different from construction and from IT ones...... etc.

i am looking specifically for how P3 is handling it. and what is better for P3? or they r equal? specially when progressing....

with my great appreciate for each word of yours.

Hello Paul

Admittingly, I haven’t tried that kind of logic yet(FS-50%) but as I used it in my sample project I noticed that it is same as using days as lag too... would there be a significant implication in terms of progress updating (compared to the usual way of using days as lag)..?? as I know there’s none in P3 like this...

Kind regards,

Christian