Hi Mike - that is exactly what I am saying!! At the present time I am working on a project for a type of plant which uses a process which is relatively new. Even after the concept stage, at pre-feasibility where, traditionally, scoping options are explored - not only is there uncertainty in some areas of the plant about which type of equipment will be used but what size any particular piece of equipment will be! Technical specifications that appear suitable early on may radically change as the maturing process design throws up new requirements. Project development in the processing/oil & gas/chemical industries is a process over a relaticely long time of a maturing design which consequently requires a maturing schedule/cost estimate. It may be theoretically correct to develop schedules from the bottom-up but in the project development I am involved in there is little point in ’Level 4’ schedules early on when you don’t have the ’Level 4’ information on which to base it.

cheers,

Omar

Hi Anoon

Precisely.

If there are a number of alternative forms of construction either plan for each as an alternative or chose the longest to start with and put in some buffers.

I do have a library of different types of construction that I can copy and paste into any new programme.

If I ever have to plan something new I always keep a copy in the library for when I may need it again.

And before anyone asks for a copy of my library the answer is no.

Best regards

Mike Testro

Hi Omar

You seem to be saying that at concept stage nobody knows what the project will comprise.

Whatever it is some one in the system will have enough detail to at least put a budget on it.

And somebody else will know how to build it.

If assumptions are to be made it is best made at level 4 with bottom up planning so that different options can be compared and evaluated.

In another thread I explained how I did a bottom up programme for a hotel based on an artists brochure.

I did three versions comparing the three potential structures - steel - insitu concrete - load bearing brick / block.

The developer could therefore proceed with realistic information.

Best regards

Mike Testro

Hi Khaled

I have just looked at your starting thread -

I build a Level 2 schedule with all activities related logically. To make the relationship between activities I had to add lags. Activities with zero Total Float are depicted on Critical Path. Which impact does the use of lags has on the accuracy of the Critical Path? Is it a prerequisite to have zero lags between activities to make a Critical Path?
I’m using Primavera ver. 6.

The use of lags completely distorts the critical path - never use them - same with SS FF links.

Your level 2 programe should be built up from a properly prepared level 4 programme.

If you don’t know how to build it - don’t try to plan it.

Best regards

Mike Testro

Steve and Dieter,
thank you both.

Dieter,
Linear Diagram (or Time-Location Diagram) is one of Spider Project standard graphical reports like Gantt Chart or Network Diagram.

Steve,
beer is fine. Please send me the examples you would like to show at the presentation.

Best Regards,
Vladimir

I must confess, Vladimir, the more I hear about Spider, the more impressed I am! I’m looking forward to meeting you for a beer (a vodka?) at PMI’s College of Scheduling Annual Conference in Boston in mid-May. (I’ll be presenting about DRAG at 9:10 am on Wednesday, May 20th.)

Was it really???

Well, they say that copying from a template is one of the most efficient ways to plan a project...

Dieter, perfectly phrased, I think! Thanks!

Fraternally in PM,

Steve Devaux

Dieter wrote:

"Independent from software, if you’ll consider what a scheduling algorithm does with lags. They are regarded equivalent to activities."

Hi, Dieter. I just wanted to tweak one statement slightly. The above is completely true when talking about lags on FS relationships. And, of course, earlier in the thread, we had established that we were recommending using FS relationships exclusively.

But I just want to point out that IF we were talking about lags on complex (fancy-shmancy?) relationships, the statement that they are "equivalent to activities" would not be completely true. Lags on FS and FF relationships are "equivalent to activities" in that they add time to the project (i.e., have their own DRAG) that is NOT incorporated in the work of either the predecessor or the successor.

But in the case of lag on an SS or SF relationship, the lag typically represents work already accounted for in the predecessor (i.e., DIG INITIAL 400m. OF TRENCH as an SS+3 predecessor to LAY PIPE). Then the DRAG is associated with the predecessor’s work. Shortening the time taken to dig the 100m. from three to two days would (should!) reduce the lag to SS+2 and, if on the CP, shorten the project by one day.

Fraternally in PM,

Steve Devaux

Dear Khaled,

I would suggest that you complete the link with using another activity instead of the lag. Call it curing time/ checking/commissioning/ of standby time.

Going down with the level of detail and using the correct sequence of work, is better than assuming how the critical path is being calculated or what is the meaning of your results.

Use simple logic and simple sequencing and you will get the logical answers that you are seeking and start using the Program more effectively to represent the actual progress on site.

Best Regards,

Samer

Dear Khaled,

You will need to make sure that your "lags" and schedule relationships are correct. If the logic of your Schedule is correct, then you can proceed with the resources and the durations, and the schedule development.

Subsequently, you will have a Critical Path. The Critical Path will have activities with Zero Float. It is the minimum time to complete the project depending on your stated activites and until schedule development.

Best Regards,

Samer

Khaled,

I don’t know P6, but I’ll try to give you an answer about general usage, independent of software package.

Using lags, in and of themselves, should have no impact on the ability to define your critical path (provided all the lag and logic are correct, of course!). The biggest problem for you with lags will likely be the need to go in and manually change the lags as either optimization or work is performed.

NOTE: This does NOT address complex dependencies (SS, FF, SF), which CAN result in "strange" happenings in critical path computations if the user is not careful. However, you don’t mention using such links.

But you say that "To make the relationship between activities I had to add lags." I confess, I don’t fully understand this. A lag on an FS (or even FF!) relationship functions exactly like an activity (and can have DRAG if it’s on the critical path). Indeed (as Mike Testro would probably point out!), any complex or lag relationship can be modeled using a combination of FS relationships, additional activities, and milestones. And the result will often be a clearer network where it’s easier to identify the big DRAG activities.

Hope that helps, though perhaps an expert with P6 will weigh in.

Fraternally in project management,

Steve Devaux