Residential Construction, ALAP
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2012年7月6日 6:38
This is about something that I did out of curiosity and now have a puzzle.
Opened an instance of a clean Residential Construction template that ships with MSP2007.
(This is also available on-line in MSP2010)
This is a good example file that I use to try things out.
It is incomplete in that there are no material type resources and no costs.
It is "incorrect" (in my view) because two tasks, 68 and 74, do not have successors.
I prefer all tasks to have at least one FS0 predecessor and at least one FS0 successor, and possibly (probably) more than one of each.
I avoid any kind of predecessor links/lag which are not FS0 (none in Residential Construction).
I never assign predecessors, resources or costs to the summary tasks (none in Residential Construction).I filled in the missing successors at line 68 and 74, so that there is a complete, closed network.
74 Paint all - 2nd floor "73,68"
79 Install 2nd floor - hall bath and private bath cabinets "78,74"In task information, I set the project finish date to 31/12/2012 and scheduled from the finish date, to see what would happen.
Usually, because I am big fan of the critical path method, I would never set the project finish date and would never schedule from the finish date, and would never schedule a task to be ALAP. I have previously known about the "strong" effect of ALAP, which is that it consumes all of the total slack on the path, not just the total slack of the task.I inserted the constraint type column into the entry table.
Tasks which are already there retain their ASAP property (I won't call it a date constraint).
The existing summaries all get changed to ALAP.
New tasks automatically pick up ALAP (checked for this).I had expected the existing tasks to all pick up the ALAP constraint, but that did not happen, so OK, new tasks only.
I changed the ASAP to ALAP for all tasks by fill down from the top cell in that column.I had also expected all tasks would now be scheduled ALAP, meaning would use up all of the slack on the path they are on, and all tasks would go critical.
This did not happen (even hit F9). Some tasks still have some positive total slack. Why? How did they escape? What am I missing?
全部回复
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2012年7月6日 16:36
Trevor,
While I will agree with some of your assumptions and discoveries, remember that this is a template, and not a final project schedule or file. In the residential template online, I do not see any missing predecessors and successors. When the template was constructed, it apparently was built in the traditional, "schedule from a start date", finish to start type approach. This means that all tasks are set to ASAP. When you change in the Project Information dialog to schedule from a finish date, any tasks that were created in the first mode remain as ASAP - although the summaries go to ALAP. Any new tasks from this point forward (while in schedule from finish date mode) will be set to ALAP.
When setting all tasks to ALAP, I find that the residential template I download from online does take ALL the float (slack) up and all tasks become critical. In my opinon, the ALAP setting is beneficial when using the critical chain methodology and when you need to set it on a task by task basis. Personally, I have never used it as a blanket setting on any project in the past 34 years, but have used it when conditions warrant.
There - you have my two cents worth and my humble opinion.
Gregg D. Richie, PMP, MCTS; Author, Microsoft Project 2010, Microsoft Official Academic Course Series
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2012年7月9日 7:31
Gregg,
Roger everything in your first para, except:
There is nothing wrong with this template as a finished project schedule except for the missing successors on tasks 68 and 74, the missing materials and the missing costs. Once the missing successors are filled in, there is a closed network and every task is on one or more paths which go from the first task to the last. Since there are only FS0 predecessors, and no FF, SS, SF or +/-lag, this should be a good testbed for observation and discussion about the constraint types, especially ALAP, and the "choice" of scheduling from the project finish date which is offered by MSP but rarely if ever used. You don't use it and I don't use it, but some do.
Also, I am interested in allowing the whole project to slide to the right and observe the change in cumulative work and the cash flow profile (cumulative cost), and to establish a range of "S" curves from earliest to latest but still within the original earliest start and earliest finish dates.I have tried this with both the MSP2007 version (the one that ships with MSP2007) of Residential Construction and the online MSP2010 version.
They are clearly different files because they have different overall durations, but I have not yet bothered to find the point of difference.
MSP2007 version, start 1/6/2012, 152 days, finish 31/12/2012
MSP2010 version, start 1/6/2012, 158 days, finish 08/01/2013In both cases, some tasks escape and retain some float. There may well be a reason (even a bug is a reason) but for me right now it just defies my expectations. Still hoping someone might jump in here.
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2012年8月16日 19:49版主
Please re-post if this is still an issue..
