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Project Flex?

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Chris Franzoso
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Joined: 28 Aug 2016
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Chris,

I agree that DRAG is one more useful indicator like different kind of floats. Floats show what happens with the project schedule if an activity is delayed, Drag shows what happens if an activity is shortened. When considering project crashing DRAGs show where to look first.  I disagree that DRAG shows the PM where to look first.  DRAG does not indicate if a task can actually even be crashed, so why look there first?  Even Steve has the DRED calculation to indicate resorce elasticity.

There is another useful indicator that we call Flex but only Spider Project calculates it, so if you are interested we can discuss it in Spider Project forum on this site.  Yes, let's discuss.

In our practice the end value is automatically calculated by Spider Project with each project update and when risk simulation is used probability to meet target values is calculated too. Project management decisions are justified by their impact on end value and probability to meet project targets. And top management requires regular reports on expected end values and trends of probability to meet project targets, so project managers cannot miss this. This is not just a theory, this is everyday practice in many companies. In Steve's books, the latest one, he disagrees with the use of monte carlo simulation.  Interested to know how you include risk simulation.

The problem that I meet most frequently is that people manage project cost but do not manage actual expenses. Project schedules include the cost (what will be paid for the job) but not expenses that reflect the real costs of project resources, indirect costs, etc. Actually most people manage their contracts but not expenses, future profits, etc. Good and educated top managers would require this but there is a shortage of wise top managers. If some top managers will read Steve's books maybe they will start to require taking current decisions basing on their impact on overall project and company goals.  I think most of the managing the future profits from a project is in the realm of portfolio management not project management.  

If you are interested how "time is money" is modeled in Spider Project start this topic in Spider Project forum.  Here it is!

Best Regards,

Vladimir

Replies

Rafael Davila
User offline. Last seen 2 hours 15 min ago. Offline
Joined: 1 Mar 2004
Posts: 4620

Spider Project displays the following Schedule Reserve values.

Schedule Reserves photo Schedule Reserves_zpsbgsbkwix.png

Here we can discuss those displayed by Spider Project but not displayed by other software [highlighted in bold].  We can discuss why displaying hours and days [not as simple as applying a conversion factor].

> Total Float – time period of potential activity delay that does not cause a delay of the
project finish or any target date set in the project schedule.

> Terminal float – the duration between planned completion and the current contract Completion Date. This is also ‘owned’ by the Contractor and cannot be used to mitigate the effect of a compensation event.

http://www.stevencevans.com/float/

> Negative Float – the amount of time that must be saved to bring the project to completion on time.

> Free Float – time period of potential activity delay that does not cause a delay of any other activity in the project schedule.
  Both total and free floats may be applied to activity start and activity finish.

> Interfering Float - is that part of the total float which causes a reduction in the float of the successor activities.

https://www.safaribooksonline.com/library/view/quantitative-techniques-t...

https://www.youtube.com/watch?v=BDZOyq2hRs4

> Independent Float - the amount of delay which can be assigned to any one activity without delaying subsequent activities or restricting the scheduling of preceding activities.

http://pmbook.ce.cmu.edu/10_Fundamental_Scheduling_Procedures.html

https://youtu.be/gOT55A_e9ps

> Relationship Slack - the amount of ‘unused’ time difference between the predecessor and the successor activities or relative float in relationships. This slack value has nothing to do with the float values or either of the two activities that it relates. It merely indicates how close each predecessor is to becoming the driving relationship for the successor activity.

http://scheduleanalyzer.com/sa_long_theory.htm

> Start Flex shows if Activity start may happen earlier with the same activity finish without changing any other dates in the current schedule.

> Finish Flex shows the potential delay of the activity finish without the moving activity start
date and that does not delay any other schedule activity.

> Super Float – the time period of potential activity finish delay without delaying the activity’s start and that does not delay the project finish date.  Super Float shows what maximum deceleration of activity execution is acceptable.

> DRAG shows an impact of the project activity on project duration.

> Assignment Float - Activity floats do not provide all the data necessary for project control. In the projects with the complicated resource assignments there may be situations when an activity has different start and finish floats. Its start cannot be postponed without delaying project finish date, although its finish can be delayed without serious consequences.  Resources are often separately assigned on an activity.  There are several types of independent assignments.  Thus, a team of resources can be assigned on an activity to do a certain amount of work, or for a certain period of time, while other resource teams perform the rest of activity work independently - earlier, simultaneously or later.

> Buffer - CCPM is based on the assumption that the critical chain can be protected by using excessively large buffers something that is impractical in most construction schedules. Too much buffer and frequently a continuously changing Critical Chain/Path It make no sense to manage buffers no longer feeding into the critical chain. Managing Student Syndrome, Parkinson law and buffers can be done without the need of specialized software if you understand CPM and Project Risk Analysis. The easiest way to do so is by comparing the finish of contractual milestones fixed in time [with no successors] in alignment with the contract to the corresponding milestone fully linked to the schedule [a tight target schedule], can be done easily if using a hammock.

http://www.goldratt.co.uk/resources/critical_chain/

All these parameters are useful for project schedule analysis and decision making.

Best Regards,

Rafael

Chris,

Rafael explained what is Start Flex. The same with Finish Flex – it shows an amount of time activity finish may be delayed without the moving activity start and delaying any other activity.

Flex shows activity duration flexibility and helps to optimize resources used for activity execution. If activity duration is flexible then it can be done with fewer or less productive resources without delaying other activities.

Other topics deserve separate discussions and so I will start them in the separate threads.

Regards,

Vladimir

Rafael Davila
User offline. Last seen 2 hours 15 min ago. Offline
Joined: 1 Mar 2004
Posts: 4620

Chris,

Start Flex shows if Activity start may happen earlier with the same activity finish without changing any other dates in the current schedule.

The following example illustrates one of the uses of Start FLEX.

  • Phase 1 shows a Start FLEX of 5 for Activity 2, this means activity start might be advanced by increasing its duration up to 5 days before any further increase stops advancing its start and start delaying its finish.
  • Start Flex when present can be displayed as a low height bar to the left of the regular activity bar.

If you increase the duration of Activity 2 on Phase 1 by 4 days you get Phase 2.

  • This advances the start of Activity 3, a successor.
  • This unusual behavior is known as Lag Drag.
  • Phase 2 shows a Start FLEX of 1 for Activity 2, this means activity start might be advanced by increasing its duration up to 1 extra day before its start is no longer advanced and any further increase in duration will delay its finish.

If you increase the duration of Activity 2 on Phase 2 by 2 days you get Phase 3.

  • This advances the start of of Activity 2 by one day and its finish by 1 day.

 photo StartFLEX_zpsiivubcda.png

Let me know if this is good enough for you to understand what Start FLEX is.

Best Regards,

Rafael