ABPSC — Codify Working Groups in P&P

As per ABPSC-52, Working Groups are currently ad hoc convenient fictions for Subgroup Chairs to organize their members into groups to perform specific tasks.

However, without clear guardrails and guidelines, they have mutated in some cases to use cases for which they were never intended.

It may be useful to clarify what a Working Group is, in the original intended sense, so that there are clear processes to follow. This definition should probably be added to the Subgroups (Section 3.7), perhaps with a quick definition in Section 2.

('Other' use cases such as described in ABPSC-52 will be supported through mechanisms yet to be determined. Defining Working Groups here does not immediately eliminate those other use cases, it simply clarifies which need special handling.)