Containment Example:

A hierarchy of student groups

A typical student cohort represents one year of a degree program. Let us suppose the following:
All students in the first year (say 30 students) attend every lecture
The students are split into 3 tutorial groups each of which attend one tutorial.
Assuming this is the only degree program in our institution we might call the year group BSc1 and the tutorial groups BSc1a, BSc1b and BSc1c.

BSc1 contains BSc1a, BSc1b and BSc1c

Consider a module which consists of one lecture and one tutorial (each).
BSc1 attends the lecture L at 09:00
BSc1a attends tutorial Ta at 10:00
BSc1b attends the tutorial Tb at 11:00
BSc1c attends the tutorial Tc at 12:00


Availability
09101112
BSc1
BSc1a
BSc1b
BSc1c
Key
Group is attending an event at this time.
Group is free at this time.
Group is not available because something it intersects with is at an event.
We refer to the last case as "vacariously attendance". Thus BSc1a does not attend the lecture as itself - it attends the event vacariously.