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Topics: Scheduling, Scope Management, Using PMI Standards, Work Breakdown Structures (WBS)
Hammock Activity
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What exactly is a Hammock Activity and how does it fit into Project Management or the schedule ? Supporting Examples would be much appreciated.
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A hammock activity (also hammock task) is a schedule or project planning term for a grouping of tasks that "hang" between two end dates it is tied to. - http://www.pmhut.com/a-glossary-of-project-management-terms

PMCHAMP.COM explains is as follows with example:

A Hammock Activity is a schedule or project planning term for grouping smaller subtasks that hang between two dates.

The sub tasks are not really related in a hierarchical sense. This means that there is no fixed sequence of tasks – any of these subtasks can be done at any time, but there is no particular sequence. The objective is to group dissimilar activities that must be performed to achieve an overall goal, but their individual sequence is not important or logical.

For example, let’s say you have an activity called “plan vacation”. It can have multiple sub tasks like “book hotel’, “get brochures”, “book tickets”, “find a guide”, “check local attractions” etc. Any of these tasks can be done first, without the other being started or completed. But there will be an overall target to complete “plan vacation” by the third quarter of the year.

The size of the hammock, or the duration of the hammock is calculated by the start date of the earliest task, and the finish date of the last task.

The name hammock activity comes from the fact that individual activities hang between the overall dates, floating, just like a hammock.

On PROJECTMANAGEMENTQUESTIONS.COM, some responses were:

A hammock activity is a grouping of subtasks that is "hung" between a start and an end date. The tasks are unrelated in the sense of a WBS and are not related in the sense of a depencency. These activities may be grouped under a very general summary heading such as "pre-project preparation" or "Q3 Plans".

The word Hammock is derived from a word used by natives of Haiti meaning "fish net".

- answered 4 years ago by sdcapmp (45,840 points)

AND

Obviously English is not your first language :). Hammock is not the name of the person, but it's this (so called) bed that you see on the beach stretching between two trees.

Now to answer your question: a hammock activity is a task or a group of tasks that stretches between two other activities. Hammock activities are flexible, the beginning of the hammock activity may change as well as its end (so, unlike other activities, a hammock activity is not time estimated). Let's assume that Task A is supposed to end on Monday, April 25th, and Task E is supposed to begin on Friday, May 6th. A hammock activity, consisting of 3 tasks (B, C, and D) begins when Task A ends, and end when Task E begins. So task B begins on Tuesday, April 26th, and task D ends on Thursday, May 5th. Now if Task A ends on Wednesday, April 27th, then task B begins on Thursday, April 28th. This is where the similarity between a hammock activity and a real hammock is prominent (it's the flexibility!), a real hammock, even if the trees are (reasonably) far from each other or very close, can still be installed.

Hammock activities are common in construction projects, where an activity has to happen between two tasks. An example of such activity is drainage.

- answered 4 years ago by MaplePM (46,940 points)
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3 replies by Francisco Yago, Rami Kaibni, and Urban Werner
Jan 24, 2016 12:28 AM
Rami Kaibni
...
Thank you Suhail - I went through all this and checked online for some other resources but for some reason I am not able to fully understand the concept and relate it as well to the network diagram.

If we have certain tasks A to G with dependencies between them, we can draw network diagram and sometimes introduce dummy activities but where does the hammock activity come in play.

If you can give me a full example I would very much appreciate it.
Oct 03, 2017 4:51 AM
Francisco Yago
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Nice and complete. The experts judgement! Thanks Suhail
Oct 17, 2017 3:15 AM
Urban Werner
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That's a good and comprehensive summary
Network:129697



Jan 23, 2016 3:28 PM
Replying to Suhail Iqbal
...
A hammock activity (also hammock task) is a schedule or project planning term for a grouping of tasks that "hang" between two end dates it is tied to. - http://www.pmhut.com/a-glossary-of-project-management-terms

PMCHAMP.COM explains is as follows with example:

A Hammock Activity is a schedule or project planning term for grouping smaller subtasks that hang between two dates.

The sub tasks are not really related in a hierarchical sense. This means that there is no fixed sequence of tasks – any of these subtasks can be done at any time, but there is no particular sequence. The objective is to group dissimilar activities that must be performed to achieve an overall goal, but their individual sequence is not important or logical.

For example, let’s say you have an activity called “plan vacation”. It can have multiple sub tasks like “book hotel’, “get brochures”, “book tickets”, “find a guide”, “check local attractions” etc. Any of these tasks can be done first, without the other being started or completed. But there will be an overall target to complete “plan vacation” by the third quarter of the year.

The size of the hammock, or the duration of the hammock is calculated by the start date of the earliest task, and the finish date of the last task.

The name hammock activity comes from the fact that individual activities hang between the overall dates, floating, just like a hammock.

On PROJECTMANAGEMENTQUESTIONS.COM, some responses were:

A hammock activity is a grouping of subtasks that is "hung" between a start and an end date. The tasks are unrelated in the sense of a WBS and are not related in the sense of a depencency. These activities may be grouped under a very general summary heading such as "pre-project preparation" or "Q3 Plans".

The word Hammock is derived from a word used by natives of Haiti meaning "fish net".

- answered 4 years ago by sdcapmp (45,840 points)

AND

Obviously English is not your first language :). Hammock is not the name of the person, but it's this (so called) bed that you see on the beach stretching between two trees.

Now to answer your question: a hammock activity is a task or a group of tasks that stretches between two other activities. Hammock activities are flexible, the beginning of the hammock activity may change as well as its end (so, unlike other activities, a hammock activity is not time estimated). Let's assume that Task A is supposed to end on Monday, April 25th, and Task E is supposed to begin on Friday, May 6th. A hammock activity, consisting of 3 tasks (B, C, and D) begins when Task A ends, and end when Task E begins. So task B begins on Tuesday, April 26th, and task D ends on Thursday, May 5th. Now if Task A ends on Wednesday, April 27th, then task B begins on Thursday, April 28th. This is where the similarity between a hammock activity and a real hammock is prominent (it's the flexibility!), a real hammock, even if the trees are (reasonably) far from each other or very close, can still be installed.

Hammock activities are common in construction projects, where an activity has to happen between two tasks. An example of such activity is drainage.

- answered 4 years ago by MaplePM (46,940 points)
Thank you Suhail - I went through all this and checked online for some other resources but for some reason I am not able to fully understand the concept and relate it as well to the network diagram.

If we have certain tasks A to G with dependencies between them, we can draw network diagram and sometimes introduce dummy activities but where does the hammock activity come in play.

If you can give me a full example I would very much appreciate it.
Network:85270



Let me clarify that. Say Activities B.C.D. and E with respective durations of 2,3,1,and 4 days duration, are all dependent on Activity A which has a duration of 4 days. Activities B, C, D, and E are also predecessor activities to Activity F. In fact the activities B.C,D, and E have no other importance to be separate activities than to distinguish them from each other and E being on critical path. What if I merge these 4 activities into one with a duration of 4 days and let us call this X activity. Then the critical path would be A-X-F, where X stands for B,C,D and E. I would go for this merging option as there is no other dependency creating another path put of this network diagram. Now these 4 activities B, C, D and E are internal affair of newly formed Activity X and it does not matter in what order they are done internally, but they would be considered as Activity X externally. These are the hammock activities. Hope I made it clear to you.
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2 replies by Rami Kaibni and TUSEEF AHMED KHAN
Jan 24, 2016 1:03 PM
Rami Kaibni
...
Thanks a lot Suhail ... I appreciate it a lot, now I understand the idea very well.

Just one comment: In this scenario you've demonstrated, activities B,C,D,E come before F so they are predecessor activities to F, not successor - Right ?
Nov 18, 2019 5:35 AM
TUSEEF AHMED KHAN
...
good explanation,
Network:129697



Jan 24, 2016 9:47 AM
Replying to Suhail Iqbal
...
Let me clarify that. Say Activities B.C.D. and E with respective durations of 2,3,1,and 4 days duration, are all dependent on Activity A which has a duration of 4 days. Activities B, C, D, and E are also predecessor activities to Activity F. In fact the activities B.C,D, and E have no other importance to be separate activities than to distinguish them from each other and E being on critical path. What if I merge these 4 activities into one with a duration of 4 days and let us call this X activity. Then the critical path would be A-X-F, where X stands for B,C,D and E. I would go for this merging option as there is no other dependency creating another path put of this network diagram. Now these 4 activities B, C, D and E are internal affair of newly formed Activity X and it does not matter in what order they are done internally, but they would be considered as Activity X externally. These are the hammock activities. Hope I made it clear to you.
Thanks a lot Suhail ... I appreciate it a lot, now I understand the idea very well.

Just one comment: In this scenario you've demonstrated, activities B,C,D,E come before F so they are predecessor activities to F, not successor - Right ?
Network:85270



Sorry, I might have mistyped. They obviously are the predecessors. I have made the correction in my last post.
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1 reply by Rami Kaibni
Jan 25, 2016 3:15 AM
Rami Kaibni
...
Thank you very much Suhail - Appreciate your input and now I do have a better understanding.
Network:1065



For your referefence, according to Project management lexicon at the below link: http://www.projectmanagementlexicon.com/hammock-activity/

Hammock activities are a set of related activities aggregated at a summary level on the project network diagram to report as a singular activity at that summary level. This helps top management to get a relevant picture of the project without digging into details that might not be relevant for that level. It apears that there might be another definition for this.
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1 reply by Rami Kaibni
Jan 25, 2016 3:14 AM
Rami Kaibni
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Thanks for your input Lih Wang
Network:129697



Jan 24, 2016 8:38 PM
Replying to LIH WANG
...
For your referefence, according to Project management lexicon at the below link: http://www.projectmanagementlexicon.com/hammock-activity/

Hammock activities are a set of related activities aggregated at a summary level on the project network diagram to report as a singular activity at that summary level. This helps top management to get a relevant picture of the project without digging into details that might not be relevant for that level. It apears that there might be another definition for this.
Thanks for your input Lih Wang
Network:129697



Jan 24, 2016 8:01 PM
Replying to Suhail Iqbal
...
Sorry, I might have mistyped. They obviously are the predecessors. I have made the correction in my last post.
Thank you very much Suhail - Appreciate your input and now I do have a better understanding.
Network:33

Gents, Thank you for this topic, it is very useful and all the answers appreciated
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1 reply by Rami Kaibni
Sep 20, 2016 2:00 PM
Rami Kaibni
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You're Welcome Vincent - Glad you found it useful.
Network:407



Just a note: Summary activity, LOE and Hammock are different types of activities. Many times i have seen people using these terms interchangeability.
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1 reply by Rami Kaibni
Sep 20, 2016 2:01 PM
Rami Kaibni
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In principle yes I agree with you but I am not sure how is LOE related to this subject at all.
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