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Hammock, LOE, summary difference

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Abbas Rajabpour
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Can someone please clarify the difference between these three types of activities because I think they are representing the same goal. I have read alot but couldn't differ.

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Patrick Weaver
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Summary Activities, LOE and Hammocks are distinctly different activity types; each has its advantages and limitations and very few tools correctly implement all three types.  A full explanation is in this paper: https://mosaicprojects.com.au/Mag_Articles/P016_Hammocks_LOE_and_Summary_Activities.pdf

Patrick Weaver
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Summary Activities, LOE and Hammocks are distinctly different activity types; each has its advantages and limitations and very few tools correctly implement all three types.  A full explanation is in this paper: https://mosaicprojects.com.au/Mag_Articles/P016_Hammocks_LOE_and_Summary_Activities.pdf

Abbas Rajabpour
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Thanks David for your reply, I am preparing myself for PMI-SP exam and in the course that I took, it was talking about these three different activities:

SUMMARY ACTIVITY

LEVEL OF EFFORT

HAMMOCK

I understand the meaning of each of them, but they seem to be different to use. Thanks for sharing your experience and thoughts on this.

david kelly
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Abbas, Because of your use of the term LOE, I presume this is a P6 query, although posted in a general forum. Level of Effort (LoE) was originally a terminology used by NASA, and the team that wrote P6 in the late 20th century seems to have worked for NASA and only ever user Microsoft Project. ‘Most’ of us still call them Hammocks. P6, in my opinion, remains a terrific piece of late 20th century software. Both LoE and WBS summary activities in P6 can have no schedule impact. WBS Summary activities are like hammocks, except they require no relationships, and will ignore them if they are present. The dates normally calculated for each activity are ignored, and a summary of the dates of every activity that shares the same WBS code is used. My most common use for them is to spread undifferentiated costs from a financial system (eg SAP) across all of the activities that share a WBS code. LoE activities use the relationships that bind them to the plan to calculate dates and durations. The relationship types that can be used are subject to extraordinary rules when the LoE activities are ‘nested’. I did have the rules for this written down 10 or 15 years ago, but cannot find them. My own choice is to use only Start to Start and Finish to Finish relationships to keep things ‘simple’ for me, but almost everything is allowed (and probably should not be). P6 is VERY poor at relationship-centric reporting.
david kelly
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Joined: 12 Feb 2016
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Abbas, Because of your use of the term LOE, I presume this is a P6 query, although posted in a general forum. Level of Effort (LoE) was originally a terminology used by NASA, and the team that wrote P6 in the late 20th century seems to have worked for NASA and only ever user Microsoft Project. ‘Most’ of us still call them Hammocks. P6, in my opinion, remains a terrific piece of late 20th century software. Both LoE and WBS summary activities in P6 can have no schedule impact. WBS Summary activities are like hammocks, except they require no relationships, and will ignore them if they are present. The dates normally calculated for each activity are ignored, and a summary of the dates of every activity that shares the same WBS code is used. My most common use for them is to spread undifferentiated costs from a financial system (eg SAP) across all of the activities that share a WBS code. LoE activities use the relationships that bind them to the plan to calculate dates and durations. The relationship types that can be used are subject to extraordinary rules when the LoE activities are ‘nested’. I did have the rules for this written down 10 or 15 years ago, but cannot find them. My own choice is to use only Start to Start and Finish to Finish relationships to keep things ‘simple’ for me, but almost everything is allowed (and probably should not be). P6 is VERY poor at relationship-centric reporting.