How to schedule resources in parent tasks for as long as the subtasks last

[Roelant Ossewaarde]

Hi all,

Consider the situation where there is an academic project that runs for a few years. One of the subprojects runs for a short period of time. I'd like to schedule a resource to provide oversight over the tasks in the subproject.  

When I use the following code, the resource workpackageManager is scheduled for the duration of the project, not for the duration of wp0. With the following code:

task project "Project" {
  task wp0 "First workpackage" {
    task oversight "Workpackage management"{
      start ${projectstart}
      allocate workpackageManager
      limits {  weeklymax 1h {resources workpackageManager} }
    }
    task task1 "Task 1" {

      allocate Scientist1
      length 1w
    }
    task task2 "Task 2" {
      depends !x
      allocate Scientist1
      length 1w
    }
  }

See the attached Gantt chart. Obviously, oversight for that work package should end whenever that work package concludes (and not whenever the project concludes). 

A relative end date for the oversight task would be helpful ("end task2{onend}"), but onend does not yield the date that "end" wants as an argument. 

I could in theory specify the end date after inspecting whatever the scheduler decided the end date of the subtasks should be, but there surely must be a less manual way?

Kind regards,

Roelant.

[Michael Howe]

Hi

Gemini chewed over this for some time and answered:

The issue here is that your `oversight` task is open-ended on its back end. Because it only has a `start` date specified and no explicit `length`, `duration`, or `effort`, TaskJuggler leaves the task unbounded. By default, it will stretch to the end of the parent container—in this case, the entire project.

To fix this, you need to turn `oversight` into a **hammock task**. A hammock task dynamically stretches its duration to exactly fill the space between two specific boundaries without needing an explicit length.

Since TaskJuggler 3, you can create a hammock task by defining a **Start-to-Start** dependency and an **End-to-End** dependency. You do this using the `{ onstart }` and `{ onend }` attributes.

Here is how you can update your code to tie the `oversight` task strictly to the duration of `wp0`.

```taskjuggler

task project "Project" {
  task wp0 "First workpackage" {
   
    task oversight "Workpackage management"{

      # Start-to-Start dependency: Starts exactly when task1 starts
      depends !task1 { onstart }
     
      # End-to-End dependency: Ends exactly when task2 ends
      depends !task2 { onend }

     
      allocate workpackageManager
      limits { weeklymax 1h {resources workpackageManager} }
    }
   
    task task1 "Task 1" {

      start ${projectstart}

      allocate Scientist1
      length 1w
    }
   
    task task2 "Task 2" {

      depends !task1 # Corrected !x to !task1
      allocate Scientist1
      length 1w
    }
  }
}

```

### **Why this works:**

1. **Moved the Start Date:** I moved `start ${projectstart}` from the `oversight` task to `task1`. This establishes `task1` as the true anchor point for the work package.
2. **Dynamic Start (`onstart`):** `depends !task1 { onstart }` tells TaskJuggler that `oversight` cannot start until `task1` starts.
3. **Dynamic End (`onend`):** `depends !task2 { onend }` tells TaskJuggler that `oversight` must finish when `task2` finishes.

Because `oversight` has no explicit duration of its own, the scheduler naturally stretches it to fill the gap between the start of `task1` and the end of `task2`.

---

**Best Practice Note:** If your work package is going to grow beyond just two tasks, it is highly recommended to use **milestones** to bracket the work. You can create a `start_ms` milestone and an `end_ms` milestone, have your tasks flow between them, and simply tie your `oversight` hammock task to those two milestones. This way, you won't have to rewrite the oversight dependencies every time you add a new final task to the work package.

Mike

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