The Glen Waverley Uniting Church PSALTER
The Salt Roster Allocation Process
This page describes how the new SALT roster allocation process (also known as an "algorithm") works. It is derived from the old Elders' Roster, appropriately modified to reflect the new parameters. Over time, it will evolve to better reflect the workings of our new church structures. The name "SALT Roster" was suggested by AlisonClarkson, following a comment by RossMackinnon that we should move away from calling it the "Elders' Roster.
Basis of Operation
The roster algorithm endeavours to equalize the allocation of duties amongst all the volunteers willing to be rostered. It looks at past allocations, and computes a "magic number" that reflects how many and how recently an individual was rostered for a duty. If you have done more duties recently than person B, you will have a higher magic number than person B. If you have not been rostered more recently than person C, you will have a lower magic number than person C. The person that has the lowest magic number and is available for a particular duty, will be rostered to that duty. These magic numbers are computed every time that the system has to make an allocation, so that they reflect an up-to-date situation.
The number of duties a particular person does should therefore balance out over a long time. While circumstances may dictate some people get a larger number of duties in a short time (for example, over summer, when many people are away and unavailable), once the vacationers return, the algorithm will try to "catch them up". (This is why you tend to get allocated more if you have been away for a month or more!)
You can see how well the algorithm is doing by checking the SaltDutyTally page. This shows the number of duties done by each volunteer for the last 52 weeks. (Previously (version 3.0) the future allocation tally was also shown, but this is now inaccurate and reflects only those allocations actually published. This will be corrected in a future version.) Note that some variations will occur, due to the changing circumstances of the many volunteers.
Allocation Horizon
The original version of the elders' roster had a fixed four week allocation, and then a tentative allocation beyond that. User feedback indicated that some people were not happy with this. For example, some people like to enter their allocations into a diary for a 3- or 6-month period ahead, and make swaps themselves if they found that their availability subsequently changed. Others were happy to look at the roster on a more frequent basis, and this allowed them to enter availability constraints in the shorter term, and allow the algorithm itself to find a replacement.
This new version (3.0) allows each salt volunteer to specify the length of fixed allocation that they want. You can change these fixed allocation times in the SaltRosterPreferences page. A more recent revision (3.1) displays only those names whose allocations are within their fixed allocation times.
Now, once your name has been published in the roster, it is your responsibility to arrange swaps. Please advise all such changes to the office if you are not confident of updating the wiki yourself. (changed in version 3.1)
Allowing variable preferences for allocation has the advantages of:
- short allocation time preferences allow you to add your unavailability at shorter notice.
- longer allocation times allow you to plan ahead, knowing that your allocation will not change in the meantime (unless you arrange a swap).
While you may change your own fixed allocation preference, note that the program will use a minimum fixed allocation preference of 4 weeks, and a maximum of 26 weeks (6 months). These lengths of time can be changed if enough people agree to the change. Why a minimum? Well, the ministry team and the office both need to know ahead of time who is being rostered, so that in the case of the office, a definitive roster for the next four weeks can be published, and in the case of the ministers, so that they can contact those on duty to inform them of any special needs. Why a maximum? Simply that this limits how far ahead the roster needs to be set up.
Why not have the same fixed allocation time for everyone? Everyone has their own preferences. Personally, I (JohnHurst) prefer to know only the next 4 weeks, since I rely upon the email reminders to keep me up-to-date, and I don't have to transfer dates to my diary. I often fill in for others at short notice anyway, and that would require changing future bookings if they stretched too far ahead. I know others prefer to have the next 6 months locked in, so that they can write it into their diaries. This variable allocation time preference caters to both groups.
If you set a long allocation time for yourself, you have the advantage that you can write these into your diary and know that they will not change without your explicit input. The disadvantage is that you have to arrange your own swaps. If you set a short time, you can be more flexible, and you help the system by being able to respond to the various circumstances that may force other salt volunteers to be unavailable, such as sickness, bereavement or other absences. The big advantage is that you can make late bindings to being unavailable, and the system will find a replacement for you, without you having to do anything.