Hammock activities

Sankar,

Hammock is a summary of detailed activities related to one another, for example, on a cut and cover tunnel structure you have a base slab, walls and roof slab and may consist of many number of bays or construction joints and depending on the length of the tunnel. You can summarize the structure by creating an hommock activity and linking the first activiy on a SS relationship and linking the last activity on a FF relationship. In P6, it is now called "Level of Effort" which basically is the same as the Hommock in P3.

Regards,

Daniel

Hi Sankar,

Daniels explanation is completely wrong. Hammock activities are not summary activities and are not level of effort activities (both of these serve quite different purposes).

A Hammock connects between two points in a schedule, and its duration is a factor of the scheduling computations (ie, the hammock has no duration of its own).  Hammocks are used to carry resources that are required for a defined function.  The best example is the tower crane on a high rise building.  It is erected when the foundations are ready and is removed after the heavy plant and equipment are lifted onto the roof. The time the crane is needed is the time it takes to get from the foundations to the roof and hoist the equipment. The Hammock calculates this duration is at any time, based on changes in underlying schedule.

Level of effort tasks have a set duration (many software tools that do not have the capability to implement Hammocks deliberately confuse the two).

Summary tasks are part of the logic structure and summaries lower level tasks within a coding system.  Hammocks are not dependent on any coding structure.

For more inforation see page 14 of: http://www.mosaicprojects.com.au/PDF/Links_Lags_Ladders.pdf  

Dear Sir,

What i understand from the usage of this  Hammock activity is mainly in Resource loaded schedule where you want to link your  Over heads ,P&M ,Preliminaries to your schedule so that the prolongation cost for any delay can be calculated directly once you update your schedule.

Regards

Sankar

Hi Sankar

Asta PowerProject creates a true hammock where similar tasks or milestones are created as "shadows" under a hammock bar.

I use it where there are different sections of a project and completion milestones are independent but contribute to the overall completion date.

I put each completion milestone under a hammock bar and link the end of the hammock bar to the project completion milestone.

Asta buffs will say that you cannot apply logic to a hammock bar but I can do it.

Best regards

Mike Testro

Patrick,

I have been using P3 since it was introduced and now I am using P6 and believed me I know exactly what I am talking about.

We used 'hammock' and 'level of effort' for summarizing activities to a higher level and you can also use it for resource loading expecially for indirect labour. So how can you say my explanation is completely wrong?

Regards,

Daniel

Simply because one software tool chooses to confuse the issue by miss applying names to 'sound good' does not change the facts Daniel - I suggest you start using proper references rather than an incorrect software manual before making incorrect assertions.  As far as I know Primavera has never included properly defined hammocks. 

On a similar vein - Henry Gantt never used what many tools call ‘Gantt Charts’ and despite Microsoft, there is a significant difference between a Precedence Diagram and a PERT chant.  See: http://www.mosaicprojects.com.au/PDF_Papers/P173_misuse-terms-gantt-PERT.pdf

I think we are all talking symantics here.

different softwear call these type of activities different things. I do not know how MS Project handles these things but I can what  p3 and p6 calls these activities. How they are used are totally up to the user.

In P3 they are called Hammocks and in P6 they are called Level Of Effort. In both cases the durations for these activities are automatically calculated. In both p3 and in p6 their predecessors must have a start to start relationship and its successor must have a finish to finish relationship.

A Level of Effort in P6 is Simialr to a Hammock in P3

A Hammock or a Level of Effort activity can be used to summarize a group of activities.

A Hammock or a Level of Effort activity can be used to spread resources over several tasks or over a long period of time such as a Project Management task or and adminstrative task.

Level of Effort uses its assigned calendars for its dates where as a Hammock activity does not

what they can not have are constraints and are not used during leveling

Zoltan's comments are fine a long as you don't mind calling an apple a pear and an orange a banana - there are significant differences between the three activity types and using the wrong name simply generates mass confusion.  See: http://www.mosaicprojects.com.au/Mag_Articles/P016_Hammocks_LOE_and_Summary_Activities.pdf

Patrick, I think that LOE defines not the type of an activity but the type of resource assignment. If assigned resource workloads are proportional to activity duration, or their hourly workloads are the same and do not depend on activity duration then we may call an activity LOE but better to call LOE resource assignments.

Patrick

I read your link. I believe that it is up to the user to determine how they want to use a hammock, a LOE or a Summarize activities.

if we are talking about P6 there is no longer a Hammock activity available this has been replaced by the LOE type of activity. 

What you refer to as the Summary activity is not even an activity is is merely a bar that summarizes a particular group of activities.

You can certainly use a LOE activity type to summarize several activities.

I agree they are three distinct things a hammock, a LOE and a Summary bar

The LOE has replaced the Hammock 

You can summaraize activities using the summary bar 

You can also use a LOE activity to summarize a group of activites. This is especially true if if is not a unique code in the schedule.

Patrick I see where you are going with using the proper names to call things and I agree with you 100%. However, everything that I mentioned above is correct.

Zoltan,

Any one can plagiarise names or call something that already exists a ‘new name’ to sound clever. What Primavera call a LOE is an approximation of a Hammock (which was the name used in P3).  The fact a single software developer decides to play around with the meaning of terms is not helpful - it is highly damaging to the emergence of any sort of professionalism in planning and scheduling. For more on this see: http://mosaicprojects.wordpress.com/2013/03/18/pert-whats-in-a-name/ (and at least Primavera is not as pathetically bad at misusing names as Microsoft).

The people that developed Hammocks in the mid 1960s knew exactly what they were creating, the term has a precise meaning and anyone, including Primavera that abuse or ignore the name are simply demonstrating there ignorance of documented facts. For more on the origins of Hammocks and exactly what the term means see: http://www.mosaicprojects.com.au/Mag_Articles/P016_The_Origins_of_Hammocks_and_Ladders.pdf

I agree with Vladimir, LOE is all about resources - a fixed level of effort for a fixed duration. Primavera can pretend differently but all this demonstrates is ignorance of Earned Value and a lack of respect for any professional standards. You emulate a LOE work package in a schedule with an activity of a fixed duration and a uniform distribution of resources.

Pat. 

Pat

We all have to work within the limitaitons of the software programs that are currently being iused on the market today. As you pointed out P6 now uses LOE so we must adapt the way we use the software and use what we have to the best of our abilities.

If that means using a LOE as a Hammock or to Summarize several tasks so be it. 

"Z"