Offsets for dependencies

The offset is the distance between two time-based dependencies. Offsets can be used to map buffers or plan work in parallel. Although offsets are a common technique in project planning, there are better alternatives in many cases.

Work packages are usually displayed as bars in project planning. Work packages can be dependent on each other in terms of time. This means that work package A must be completed before work package B begins. In this case, the work package bars are connected by arrows in the project planning to show their temporal dependency.

The Offset determines the distance between two interdependent work packages.

For example, if the offset is +2 days, the successor B starts two days after the end of the predecessor A. If work package A ends on Tuesday, work package B starts on Friday in this case. Wednesday and Thursday therefore form a buffer of two days, which is called an offset.

An offset of 0 days means that successor B starts immediately after the end of predecessor A. As project planning works to the day, B therefore starts on the day after the end of A. For example, if A ends on Monday, B starts on Tuesday.

An offset of 0 days is the standard setting for dependencies. In other words, an offset of 0 days means that no offset is used.

If the bars of work packages A and B were drawn directly behind each other, they would abut. The distance between the two bars is 0.

A positive offset means that there is a time gap between the work packages.

For example, an offset of +1 day means that there is one day between the end of A and the start of B. An offset of +2 days means two days in between, and so on.

An application example for positive offsets is to create a buffer between work packages. If work package A takes longer than expected, the planning for B can remain unchanged thanks to the buffer in the offset. A buffer can be used to compensate for delays.

Assume work package A ends on a Monday and an offset of +2 days is set. Then work package B starts on Thursday. Tuesday and Wednesday are therefore the buffer days. This buffer is deliberately planned in to compensate for possible delays in work package A.

If work package A is delayed by one day, A now ends on Tuesday. In this case, the offset can be shortened from +2 days to +1 days. Work package B can then still start on Thursday.

Another application example for positive offsets is to schedule the drying time of a workpiece. For example, if it takes two days after the end of work package A for the workpiece to dry, an offset of +2 days is set.

A negative offset, on the other hand, means that work package B begins before work package A ends. With an offset of -2 days, B starts two days before the end of A, which means that the two work packages overlap by two days. The connecting arrow points to the past.

For example, if work package A ends on a Monday and an offset of -2 days is set, then B starts on the Friday before. The two work packages therefore overlap on Friday and Monday.

Work package B can start before the end of work package A if at the end of A only activities that do not affect B are still pending.

For example, if there is only work to be done on Friday and Monday that has no influence on work package B, B can be started on Friday.

What about weekends and public holidays? In general, weekends and public holidays such as Christmas are not counted. They are treated as if they did not exist. As can be seen in the screenshot above, with an offset of +2 days, the days Saturday and Sunday are not counted.

The above scenarios sound plausible, but is the use of offsets effective or ultimately problematic?

An important aspect of project management is to communicate and document decisions transparently. But doesn't the use of offsets lead to a lack of transparency? How do you know that the positive offset should be a buffer or that the workpiece should dry? Where is it documented that only things that do not affect B will take place in the last two days? Without transparent documentation, how do you check that work package A will run exactly as required for a negative offset?

When time is running out, this is the worst possible time to suddenly get to grips with the details of work package A and consider how to organize the processes within work package A. Transparency is always created with foresight so that you can fall back on modular planning when the pressure increases.

There are alternatives to using offsets that offer more transparency.

It is easily possible to avoid negative offsets. This can be done as follows:

Work package A is divided into smaller sub-work packages, A1 and A2. It is assumed that there are various tasks in the work package that can be assigned to either A1 or A2.

A1 is decisive for the start of work package B. All tasks in A2 are not relevant for the start of B.

For example, 7 of the 10 tasks are necessary for the start of B and are therefore incorporated into sub-work package A1, the remaining 3 tasks into A2. This means that work package B is only time-dependent on A1, but not on A2.

In the end, you have two clearly defined sub-work packages. A1 contains all the necessary prerequisites for B, while A2 contains the remaining tasks. In this way, the dependency on B is limited exclusively to A1, which leads to clearer documentation and increased transparency.

An alternative to using positive offsets is to dispense with the planning of work package A completely. Instead, this work package is planned indirectly by A1 and A2.

By splitting it into sub-work packages, an explicit buffer can be planned. A2 can serve as a buffer that can be shortened or deleted if necessary in order to document adjustments.

A sub-work package called "Drying workpiece" can represent the drying process, which creates transparency instead of just using a connecting arrow that is not meaningful enough.

Offsets are a common technique in project planning, but on closer inspection they have pitfalls, especially in terms of a lack of transparency and documentation. In general, however, offsets make sense if all those involved understand and can comprehend the reasons for them.

A typical example is a work package called "Paint workpiece". If the drying phase afterwards always takes two days and everyone is aware of this, a positive offset of +2 days would be appropriate, as the alternative method would mean unnecessary administrative work.

For more complex planning, however, structured alternatives such as splitting into sub-work packages are a good idea, as they enable clearer documentation and better traceability.

Octaved Flow can handle both positive and negative offsets. There are also several levels to implement the alternatives described above. One level below work packages are tasks and sub-work packages that can be used for further allocation.

In Octaved Flow, offsets can also be used in a completely different context. For example, a task can be scheduled to take place on the third day of a work package. Strictly speaking, this is also a positive offset, i.e. from the task planning relative to the parent element, the work package, with an offset of +2 days.

Octaved Flow makes the planning process transparent and comprehensible for everyone involved, especially when working with the alternatives mentioned.