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ADM Software

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In my experience non-planning folk understand ADM better than PDM and consequently buy in to the programmes more. This is essential to achieving milestones.
Which is the best tool that supports ADM?

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John Cornish
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Hi Bernard,

Just wanted to pass on the news that Micro Planner X-Pert enables PERT diagrams to be draw with "Activity on the Arrow" (ADM) as well as PDM.

Cheers
John
Bernard Ertl
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Hi anonymous forum guest,

The start node event and activity early start are equivalent by definition. It is not possible within the context of the ADM scheduling definition to have an activity with an early start later than the time of it’s start node event.

If you have some software which works as you describe, I would suggest that it is implementing the resource constraints incorrectly - breaking the logic of the ADM network.

The only way to schedule the framing and rough piping tasks to exhibit the independent movements described by Ron & Tomas would be to modify the logic so that there is no dummy task bursting from the framing task’s start node.

(1)---Pour Deck---(2)---DUMMY---(3)---Frame Wall---(8)
......................................|
......................................DUMMY 2/5
......................................|
(4)-Deliver Piping-(5)-Rough Piping-(6)-Install Fixtures-(7)

Then a resource constraint may affect E(3) without disturbing any other tasks (directly).

Bernard Ertl
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Bernard,

Tomas is correct is stating that the start node and activity are separate and may have differing start dates.

eg:

If a constraint is placed on the activity through the resource being delayed through a change to the calendar then the ES of the start node will be driven by the dummy (and subsequent path) and not the activity.

But as I said in an earlier post the workaround is so simple that it is an irrelevance.

Bernard Ertl
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    You are saying "In the diagram presented, ES(2,5) [the dummy] = ES(2,3) [framing] because both are dependent upon E(2)." E(2) is the early time for node 2. Note that it says: dependent upon E(2).


Semantics again. I could just have easily said (and probably should have said) "equivalent to". The definition for ES(i,j) is E(i) (as posted previously and quoted directly from the text).

You are suggesting a mysterious post processing that adjusts tasks after the critical path calculations are completed and which is not consistent with the definition of ADM critical path scheduling.

In order for any possible resource levelling / calendar adjustments to remain consistent with the ADM critical path definition, they would need to occur as part of the calculations - not a post processing step.

Otherwise, the same argument could be used to distort a PDM schedule after the calculations are completed.

    And also, why not the other way around? Why the start of activity Frame Wall is the one that is dependent on the start of the dummy activity? or for that matter any other activity that bursts from the same node? If we had 10 activities bursting from the same node, which one would determine the start of others? Or any delay on any of the activities will delay the start of all the others? What a beauty!


As I mentioned already, the word dependent is misapplied in this situation. All activities (including dummies) bursting from the same start node will have equivalent early starts by definition.

ADM allows for the possibility of assigning multiple actual tasks (not using dummies) to a single start node which would be necessary for the case you are describing if I understood you correctly, but this is not what we are discussing. Through the use of dummies as laid out previously, it is possible to translate any PDM scenario of 10 SS relations correctly into an ADM "equivalent" (where it is possible to restrain/delay the "successor" activity without impacting the "predecessor" activity).

Bernard Ertl
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Tomas Rivera
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Bernard:

I think we are making progress.

You are saying "In the diagram presented, ES(2,5) [the dummy] = ES(2,3) [framing] because both are dependent upon E(2)." E(2) is the early time for node 2. Note that it says: dependent upon E(2).

Then you are saying "... Any delay on the ES of the framing activity is a delay on the dummy ...". This is diferent from the above paragraph. Any delay of the dummy is caused by any delay of node 2, not by any delay on the start of activity 2-3. These are two diferent things.

Or, if we put it in another way, where in your referenced book does it say that the early start of any activity is calculated from the early start of any other activity bursting from the same node?. Note that I am not saying the early time of the node, but the early start of the activity.

And also, why not the other way around? Why the start of activity Frame Wall is the one that is dependent on the start of the dummy activity? or for that matter any other activity that bursts from the same node? If we had 10 activities bursting from the same node, which one would determine the start of others? Or any delay on any of the activities will delay the start of all the others? What a beauty!

Tomas Rivera
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Bernard Ertl
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Tomas,

It is a pleasure to discuss the subject with you. I appreciate you staying on topic and taking the time to do some research in order to carry on. Having spent a good part of the last decade programming scheduling engines, this is a topic of keen interest to me.

I do not have a copy of the book you referenced handy, so I will reference a free, on-line source for my part (Project Management for Construction: Fundamental Scheduling Procedures by Chris Hendrickson, Department of Civil and Environmental Engineering, Carnegie Mellon University). You may check either source you prefer for verification.

According to Chapter 10.3 (Calculations for Critical Path Scheduling):
    The earliest event time algorithm computes the earliest possible time, E(i), at which each event, i, in the network can occur. Earliest event times are computed as the maximum of the earliest start times plus activity durations for each of the activities immediately preceding an event. The earliest start time for each activity (i,j) is equal to the earliest possible time for the preceding event E(i):

    (10.2) ES(i,j) = E(i)

    The earliest finish time of each activity (i,j) can be calculated by:

    (10.3) EF(i,j) = E(i) + D(i,j)

    Activities are identified in this algorithm by the predecessor node (or event) i and the successor node j. The algorithm simply requires that each event in the network should be examined in turn beginning with the project start (node 0).


All activities with the same i node will have the same ES. This is essentially the same thing you quoted:
    "In the forward pass computations the maximum of the EFD (early finish dates) values for all activities merging at a node was taken as the single ESD (early start date) value for all the activities that burst from the same node. This fact allows the assignment of this maximum number to the node itself as the early time of occurrence for the event that marks the beginning of the following activities."
But your conclusion is incorrect. In the diagram presented, ES(2,5) [the dummy] = ES(2,3) [framing] because both are dependent upon E(2). The calculations will propagate the ES of the dummy to the rough piping activity. You wrote:
    Using the example mentioned, the start of dummy activity 2-5 does not depend on the start of activity Frame Wall 2-5, its start depends on the latest finish of the activities merging into node 2.
To be 100% clear, I am not saying that the start of dummy activity 2-5 depends upon the start of activity Frame Wall 2-3. I am saying that they are one and the same. Any delay on the ES of the framing activity is a delay on the dummy unless the implementation breaks the ADM critical path definition.

Bernard Ertl
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Tomas Rivera
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Bernard:

Let me give it one more try. I went to my library and looked for an old book Precedence and Arrow Networking Techniques for Construction, 1978 by Robert B. Harris. All the quotes used will be references from this book. I will demonstrate that the start of activity Frame Wall does not determine the start of activity Rough Piping (or the start of dummy activity 2-5 for that matter).

I am going to start by saying that the fact that if two activities have equal early start date, it does not mean that one determines the other. It does not mean there is a start to start relationship.

Let us state some basic concepts for the ADM (Arrow Diagraming Method, or Activity on the Arrow method) method. "... the activities fell on the links (arrows) and the interrelations between activities were assigned to the nodes." This is saying there are two distinct elements. Nodes and arrows. Nodes are not part of the arrows. Therefore nodes are not part of the activities. Therefore, node 2 in the example mentioned numerous times, is not part of the activity Frame Wall. It only determines the earliest time it can start. If the activity is identified by the node numbers, it is only derived from a naming convention.

"In the forward pass computations the maximum of the EFD (early finish dates) values for all activities merging at a node was taken as the single ESD (early start date) value for all the activities that burst from the same node. This fact allows the assignment of this maximum number to the node itself as the early time of occurrence for the event that marks the beginning of the following activities." From this statement you can see that the early start date of any activity is determined by the latest early finish of the activities merging at the beginning node of the activity. The start of any activity does not depend on the start of any of the activities bursting from its beginning node. Using the example mentioned, the start of dummy activity 2-5 does not depend on the start of activity Frame Wall 2-5, its start depends on the latest finish of the activities merging into node 2. To be more specific, the start of Rough Piping does not depend on the start of Frame Wall.

I can go on citing statements and calculations from the referenced book that show the same conclusion. If you make the computations using the example arrow network with durations for everyone of the activities equal, for example one or two days for each one, you can see that the late start date for activity Frame Wall would be at a later date than the late start date for Rough Piping. This should show you that the start of Frame Wall does not determine the start of Rough Piping.


Tomas Rivera
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high performance construction projects.

Bernard Ertl
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Tomas,

Fair enough.

In the event of a resource calendar / levelling "constraint", the ES for the framing activity will be delayed. Unless the implementation of the resource calendar / levelling algorithm breaks the rules of the critical path relationships, the ES calculated for the start node of the framing task will still be a driver for the ES of the dummy connector and on through to the rough piping task.

I still fail to see where the ADM & PDM constructs will yield different results.

    Now to the main point of discussion: the activity Rough Piping will be scheduled for inmediate execution since there is no problem with its own resources and its only predecessor (Dummy 2-5 that comes from the finish of activity Pour Deck) is already completed.


In the ADM schema, the start node for the dummy and the framing task are one and the same. The ES calculated for both tasks should be the same. This will propagate through to the dummy’s successor (rough piping).

Bernard Ertl
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Tomas Rivera
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Bernard:

In a way you got me and I am sorry. Let me explain and expand my point.

If the job advances: your deck is poured, and we have a strike of carpenters that prevents activity Frame Wall to start. At this point you update your schedule, you do not know how long the strike is going to last, but you know you will have a delay from this point forward, and you need to take this into account somehow. You decide to reflect a tentative delay of one month to the availability of the resource carpenter. To be true with reality you need to do just that: show a delay of one month to the availability of this resource. The proper way to do this is to adjust the calendar of this resource (I acknowledge that this, in a way, is a constraint). When you do your calculations, the activity Frame Wall will try to be scheduled when there are resources available (you need to do resource leveling in order to represent the reality of your jobsite). Since there will not be resources available for one month, this activity will be delayed one month. Now to the main point of discussion: the activity Rough Piping will be scheduled for inmediate execution since there is no problem with its own resources and its only predecessor (Dummy 2-5 that comes from the finish of activity Pour Deck) is already completed.

Now, we might have a problem in modeling this exact reality if we do not have a software that has the proper features like resource calendars or resource leveling. If we do not have this feature in our software we need to resort to something equivalent that gives us the same result. This could be done by adding a predecessor to activity Frame Wall named Carpenter Strike with one month of duration, and you will obtain the same results as in the previous paragraph.

I hope I made a clear explanation and did not make a statement that might not be true in every condition. In other words, I hope that the main message is understood.

Tomas Rivera
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Bernard Ertl
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    If you delay activity Frame Wall in the ADM model (without changing logic o adding constraints, of course), activity Rough Piping will not be delayed; hence, you will have diferent dates.


Tomas, I think there is a problem in communication. How do you delay a task/activity without changing logic or adding a constraint?

Bernard Ertl
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Tomas Rivera
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Bernard:

I hate to say it but, I agree with Ronald almost in everything he has said right since his first post.
The main point Ronald is stating, is that Frame Wall does not determine any date for Rough Piping. Frame Wall´s predecessor does, but that is a whole diferent situation although calculation gives you same dates in the case of no delay. If you delay activity Frame Wall in the ADM model (without changing logic o adding constraints, of course), activity Rough Piping will not be delayed; hence, you will have diferent dates.

It is possible, I do not rule this out, that there is a communication problem here, as you implied. Ronald and myself might be looking at the same side of the problem, and you might be looking at another side of the same problem. And we do not get to understand each other. But I find this possibility very unlikely in this case.

I would be eager to have someone to demonstrate my mistake in this seeming simple and basic scenario, but of great consequences.

Tomas Rivera
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Bernard Ertl
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Ron, which statement specifically do you disagree with?

I think you are hung up on the semantics. Do you not see the logical equivalency of the implementation?

Bernard Ertl
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Ronald Winter
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Lets just say that I disagree with your previous statement. In the ADM example, Framing is a predecessor to nothing, no matter how much you want it to be.
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Sometimes, it is difficult to break down the barriers of semantics and communicate an idea effectively. IMHO, communication is as important to effective project management as any other aspect. OK. Back on topic...

In the ADM example you described, any task or calendar constraint that you add as a predecessor to the framing task will effectively become a predecessor to the rough piping task as far as the calculations are concerned.

In this sense, I likened the framing task to a PDM SS predecessor to the rough framing task. It is not technically a predecessor in the pure sense of the word. The dummy connecting the start nodes is a predecessor to the rough piping task. But it’s predecessors are all the predecessors of the framing task - a logical equivalent to the PDM SS structure.

    Delaying framing has no effect on the start of rough plumbing.
I contend that it will. Lay it out on the diagram and you will see that what I wrote above holds true.

Bernard Ertl
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Ronald Winter
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I must be misunderstanding what you are saying. Are you saying (using my ADM example below,) that framing is the predecessor to rough plumbing? It is not. Pour Deck is the predecessor to both framing and rough plumbing. Delaying framing has no effect on the start of rough plumbing.

In a PDM situation using a SS relationship from Framing to Rough Plumbing, you statement would be correct (which is my point.)
Bernard Ertl
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    In this case, ADM says no delay to plumbing, and thus no project delay.


Wrong! Adding a constraint to the framing activity in the example you provided would delay both the framing and rough piping tasks in both the ADM & PDM versions. The ES of both tasks are determined by the longest path / latest constraint on the predecessor activity (framing) in the absence of an overriding constraint/relationship directly on the succesor (rough piping).

Bernard Ertl
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Ronald Winter
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Construction delay claims is such a precise issue that it is very difficult to say exactly what you mean in short, concise statements that apply to all situations.

In the event of a Carpenter’s strike, you would be allowed to add the constraint to the framing activity. What you would generally not be allowed to do is to say, “Everyone knows that the plumbing would also be affected by the strike so I am going to add an additional constraint there as well.”

The logic in the schedule did not support this second modification. Perhaps you never did intend to wait on the carpenters before starting on the plumbing and now you want to take advantage of this situation to hide your earlier mistakes and delays.

In this case, ADM says no delay to plumbing, and thus no project delay. PDM would have shown a logical reason for the Carpenter’s strike delaying the completion of the project, thus excusable and perhaps compensable extension to the project.
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Ron,

    You say that your ADM work-arounds give the same calculated dates.


To clarify, I only claimed the SS workaround calculated equivalently to the PDM construct. I clearly stated that there is no logical equivalent to the PDM SF & FF constructs.

    You are partially right. In most cases, they give the same early dates.


AFAIK, the ES & EF are calculated the same in all cases. Do you know of a scenario in which they are not?

    THEY DO NOT GIVE THE SAME LATE DATES.


With a fixed endpoint to the schedule, and equal ES & EF, the LS & LF calculations should be identical.

    The backward pass never passes through the activity that should be driving the schedule.


I do not understand that statement. The backwards pass calculations (in both ADM & PDM systems) subtract task durations from the LF. The LF anchor point is the largest EF from the forward pass. The successor logic is identical in both schedules. The durations do not fluctuate. Both systems will calculate the respective SS structures equivalently.

Bernard Ertl
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Ron,

OK, I can just about understand your argument. I certainly agree with the late date statement especially regarding F-F relationships. But still find the matter trivial with regard to my (company’s) requirements

What does intrigue me though is your statement that ’the entire construction industry is unable to simply add constraints or even change the logic in these situations.’

If there was a strike if you aren’t able to add a delay to the programme to show that, how on earth do you show the impact of the strike, show a realistic new completion date or recovery scenario? Surely when you update the programme the information must show the reality of the construction project to date - consequently on completion the programme deviations for the baseline show the history of the project.

Re: Your idea to try to publish the study findings - Thanks for that, I am in the middle of writing a ’planning related’ paper but it is frankly a mess! Your idea sounds is a far more suitable subject matter.
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I have been wracking my brains on a way to say this clearly and succinctly and I finally got it. You say that your ADM work-arounds give the same calculated dates. You are partially right. In most cases, they give the same early dates. THEY DO NOT GIVE THE SAME LATE DATES.

The backward pass never passes through the activity that should be driving the schedule. Thus, the total floats for the ADM network do not match the total floats for PDM network; pay the man with the negative total float.
Bernard Ertl
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Tomas,

Thanks for joining in!

I still do not understand how a PDM system is scheduling the network any differently than an ADM system. AFAICT, both systems will calculate the task availability exactly the same. Both systems will calculate the successor task’s ES to be equal to the predecessor’s ES in the absense of an overriding relationship. If the predecessor slips, the successor will slip as well.

...

OK. I just had an epiphany. Ron, I think you are talking specifically about an arrow diagramming chart versus a precedence diagramming chart for displaying a logic network versus the schedule calculations / Gannt charts that would result from calculating either network? In that sense, I would agree that the listed ADM structure is not an exact representation of the PDM SS relationship. However, the practical effect of using either system would be as I described (equivalent calculations).

PDM charts which only use FS & SS relationships can be described equivalently with an ADM chart if all relationships are described using dummies, but this would not be practical for humans.

Bernard Ertl
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Tomas Rivera
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Guys,

May I jump into your conversation?
In general, I agree completely with Ronald. To me his example is very clear. Just one point of discrepancy: I do not see any SS look-alike modeling in the ADM example. To me, there is non whatsoever. Frame Wall is completely independent from Rough Piping. It does not matter whether Frame Wall is started or not.

I do agree that a real (not imaginary) SS relationhip in a PDM network will make a whole different situation in the case of a strike or a simple delay of Wall Frame. I also agree that the logic should reflect the exact nature of the job as much as possible. We should not make patches along the way a we see fit from changing conditions. The original logic should take that into account by itself. If not, our schedule is not a proper representation of what happens on the jobsite. This is where the proper tool and the ability of the user can produce a true decision making model.

Tomas Rivera
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Let us look at this logically and theoretically.

1) ADM only uses Finish-to-Start (FS) relationships. Period. There is no other relationship allowed. When all predecessors to a node are complete, then all successor activities to that node can start. You cannot gauge logically when an activity starts, only when the preceding node has all predecessors complete.

PDM, on the other hand allows you to logically gauge when the activity starts (via a Start-to-Start (SS) relationship.) It has more functionality than the ADM ‘equivalent.’

2) ADM also does not have a facility for logically overriding the CPM calculation based upon when an activity finishes. You can not tell an activity to finish only after some other activity has started or finished.

PDM has such a facility with the Start-to-Finish and the Finish-to-Finish (FF) relationships. You can logically delay the start of an activity by defining when it may finish.

Will you concede that if two things exist and one of them has more functionality, then they are not equivalent? The difference may not appear important to you, but believe me, it is important in claim situations.
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Ron,

I am trying to understand your point and would appreciate if you could elucidate your point better as I still do not understand your claim that a PDM system schedules the scenario any differently than an ADM system. Any response to my last post?

Bernard Ertl
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Ronald Winter
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What a great idea; simply post a constraint where the logic fails to accurately reflect the real-world consequences. We could do that on all activities and eliminate all of those pesky relationships that only get in the way anyhow.

Seriously, there is nothing wrong with ADM, especially if you do not care about the legal ramifications that I was speaking of. Unfortunately, the entire construction industry is unable to simply add constraints or even change the logic in these situations. It is important for Construction Schedulers to understand this before it happens to them instead of after and wish that they had.

Your experiences with your study and findings would make an excellent article for a serious journal. Have you considered writing it up and submitting it to the Association for Advancement of Cost Engineering (AACEi)? I just looked it up and the Editor of their journal (Cost Engineering) is Marvin Gelhausen, e-mail: mgelhausen@aacei.org (phone: 800.858.COST ext.: 111).
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Ron,

In the event of the strike, as I said, you could simply impose a new constraint date on event 2 that would show the delay to both activities.

I’m not assuming ADM is ’good’ or PDM is ’bad’ We were swayed to change to ADM as a result of feedback from a local study into project success/failure. A major criticism was that people did not have visibility of the project - This despite all project information being readily available. On further investigation, it was realised that the programme plans were not being reviewed as they were considered ’hard to read’ at detailed level. From this we undertook an excercise and created various programmes (about 100 activities) in as many PDM, ADM & Gantt formats as we could get hold of. The result was an overwhelming preference for ADM. As I stated in an earlier thread this may be relevant to the industry sector but within my field (electronic R&D) everybody is responsible for the ’project management’ of their own activities and consequently they need to know what’s going on.
X-Pert is the only software I found that supports ADM which is why I may sound like an advocate of it - that wasn’t the intention - just to state the flexibility of the software if you were so concerned about the triviality of s-s relationships.
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Ron,

I’m still not sure I’m following you. With either ADM or PDM, and the scenario you laid out, completing the two predecessor tasks (Pour & Deliver) would allow both the framing and piping tasks to be scheduled to start immediately on the timeline. In the absense of any calendar constraint on the framing task (to indicate a delay such as a strike), both tasks will continue to be scheduled as available starting on the timeline (through successive updates) until progress/completion/rescheduling occur. If you introduce a calendar constraint on the framing task, the piping task will be affected as well.

Bernard Ertl
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Ronald Winter
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The difference between a PDM SS relationship and an ADM look-alike is is how they function in certain delay situations. Here is an ADM example:


(1)---Pour Deck---(2)---Frame Wall---(3)
|
DUMMY 2/5
|
(4)-Deliver Piping-(5)-Rough Piping-(6)-Install Fixtures-(7)

(Note: Planning Planet Edit routines will not let me add spaces enought to make the Dummy go from Node 2 to Node 5.)

The above figure represents a SS relationship from Frame Wall to Rough Piuping. Let us say that the bottom chain of activities denoting plumbing is the critical path, with pouring the deck close behind.

Now, what happens to the schedule when Carpenters Local 234 goes on strike (assuming everyone crosses the picket line?) Wall Framing does not start. The deck is already poured and the piping is delivered. This schedule says that Rough Piping may proceed. A PDM schedule would have shown the Rough Piping being delayed with the wall framing.

In ADM, the above situation is not a project delay. In PDM, you have a logical description of the cause of project delay. THAT is why this is ADM ‘work-around’ not a Start-to-Start relationship equivalent to PDM.

On the second point, you are once again assuming that ADM is ‘good’ and PDM is ‘bad.’ A ‘non-planning’ person can not read an ADM schedule any better than PDM schedules. One good, time-scaled PDM logic diagram is worth a thousand words. Most uneducated ‘Schedulers’ just don’t take the time to produce them (or do not know that they exist) and just make a MS Project-like print dump.

On a third point, why sound like an X-pert sales person and hide behind the Guest mask? Sign-up! Log-on! Stand up to the plate.
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Furthermore,

X-Pert offers you the opportunity to have both ADM and PDM on the same network if it were essential to have one of the types of relationship to which you refer.
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Ronald,

I am struggling to understand under what circumstances you would want this exact S-S relationship as the preceeding finish and suceeding start dates are essentially contiguous Otherwise, I would simply impose a start date on the event if any delay were needed. Unless you wanted to show a lag there is no need for a dummy at all.

Similarly F-F relationships are normally a constraint on the start of a succeeding task and driven by the longest path not just the one activity. Again no dummies required.

S-F - I have never used seen the need to use one (but I’m sure you’ll advise of such circumstances that you would!)

I really don’t understand your earlier comments regarding activity ID’s - could you elucidate?

Finally can you comment on whether you think there is any merit in my earlier premise that it is better to have a programme that a ’non-planning’ person, involved in that project, can easily read and understood, or should the PM and the Planners be the only ones privy to such info?
Bernard Ertl
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Ron,

[quote]In certain cases, you will calculate out the same early start days and in other cases, it will be different.[/quote]

Could you provide an example where the calculation will be different?

Any delay on the start of the predecessor will delay the start of the successor in the arrangement I described.

Bernard Ertl
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Ronald Winter
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What I am trying to say is that your arrangement does not ACT like a SS relationship in ways that a PDM activity acts. In certain cases, you will calculate out the same early start days and in other cases, it will be different.

Assuming that all predecessors are complete before Activity X-Y, does the delay in starting a predecessor Activity X-Y delay the start of it’s SS Relationship successor Activity Y-Z? No. Activity Y-Z can begin anytime.

This is where the ‘rubber hits the road.’ These situations are real and of vital importance to delay claim analysts. In a claim situation, did your preventing me from starting Activity X-Y delay the critical Activity Y-Z? In ADM it did not logically do so. It would have been so if you were using PDM. In this case, using ADM just cost you thousands of dollars.
Bernard Ertl
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Ron,

Thanks for being willing to discuss the topic.

I’m not sure I’m following your argument. In a PDM construct, the early start (ES) of the successor task will equal the early start of the predecessor task (in the absence of another overriding relationship). The calculation is literally:

ES(k) = ES(i) + SS(i,k) for preceding task i with a SS relationship to k

The same exact calculation is achieved with the start node dummy between two tasks in ADM.

As far as I can tell, the only difference is in the terminology used to describe the relationships, not the actual implementation.

Bernard Ertl
InterPlan Systems Inc. - Project Management Software, Project Planning Software
Ronald Winter
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Bernard,

I am afraid you are confusing looks with deeds. You can place a dummy activity from the start node of one activity to the start node of another activity. This LOOKS like a Start-to-Start (SS) relationship. It is not.

In PDM a SS relationship means that the successor cannot start until the predecessor starts.

In your example, I can start the dummy anytime all predecessors to that node are complete and I can start the successor activity immediately after that. No where is the start of the original predecessor activity required in order to start the successor. This is not the same thing as a PDM SS relationship.
Bernard Ertl
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Ron, IMO, ADM does offer a direct equivalent to SS relationships in PDM networks through the use of a dummy activity/tie. I’m not sure if you were being a semantic purist in your post (ie. no direct equivalent without dummy ties), but an ADM network can offer a direct equivalent to a PDM SS tie (that acts the same as a PDM SS relationship).

I posted a simple comparison of ADM & PDM scheduling constructs in this Critical Path Logic thread.

Bernard Ertl
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Ronald Winter
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Proponents of ADM seem to assume that ADM has the same capabilities as PDM. This is just plain wrong. ADM has one and only one relationship; Finish-to-Start (FS.) PDM has four different types of relationships. You can’t do Finis-to-Finish (FF,) Start-to-Start (SS,) or Start-to-Finish (SF) relationships in ADM. You can make networks that look like these things, but they will not act the same as they do in PDM. You cannot delay the finish of an ADM activity, only the start. You cannot halt the start of an ADM activity until another starts.

Your other argument, that the logic is obvious from the Activity ID only holds true in small networks. As both nodes must be expressed in the Activity ID, the size of the ID grows very rapidly with added activities. When you get up to 10,000 activities, you have 10-digit IDs and spotting the exact match from the end of one ID in the beginning of another is almost impossible to do.
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You missed the point entirely! Whether or not the updating is cumbersome (which is debatable,) the whole point of moving to ADM supporting software is that the end-users (the assigned resources) understand the plan better than when in PDM or Gantt format.I admit though that the industry sector is relevant to this argument.

Although still in the early days, we have had far more comments/discussion about the programme than before - this has got to be a great improvement.

At the end of the day what sort of project is more likely to be completed on time? a plan that everybody buys into or one that only a planner and the PM/development manager do?

I personally think ADM was dropped by the software suppliers as PDM/gantt was an easier combination to automate multi-level programmes - I haven’t seen one that works particularly well anyway. Does anyone actually know?
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You would need to worry about the dumy activities when updating the activities with actual data. I find this update to be cumbersome. This is the reason I do not use ADM anymore, and probably the reason why High End PM Software have dropped the ADM after it was an option.
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Thanks,

First impressions of Xpert is that the ADM diagram as a presentation tool is excellent and simple to construct.

Also you can customise reports - which is a novelty.
Ronald Winter
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I did some research on your suggestion. The actual name of the software is Micro Planner X-Pert and it can be run in ADM Mode (as well as PDM.) The scheduling module sells for $2,000 US. The cost module goes for an additional $700. You can find out more at www.microplanning.com. I dont know anything more about it other than this.
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Microplan Xpert is the only one Ive come across. Very strong in some areas - weaker in others.