|Shon Feder, Gabriela Moreira||2022-05-24|
Table of Contents
- Summary (Overview)
- Context (Problem)
- Options (Alternatives)
- Solution (Decision)
- Consequences (Retrospection)
In the context of the distributed development of Apalache
facing repeated friction around unplanned work and lack of agreement on priorities
we decided to adopt an Action Priority Matrix
to achieve shared understanding and agreement on prioritization
accepting the additional overhead required by scoring and evaluating our work items.
In recent months, we have repeatedly encountered conflicts over prioritization of our work. Different members within our team, or different stakeholders outside of the team, have voiced opposing views on what work items deserve focused and urgent attention. In reflecting on these occasions in our meetings, we have come to agree that these conflicts are due, at least in part, to lack of a clearly established framework for assessing, communicating, and recording the priority of work.
In particular, when plans change, or when urgent, unplanned work needs attention, we would like a lightweight framework for reaching consensus on the new priorities, and deriving a new ordering of the work to be done.
The decision to adopt an action priority matrix for prioritizing our work was reached in December of 2021, but we weren't clear at that time how to we would determine the scores for each work item. This ADR aims to outline and codify the approach we will use.
In this document we talk about "items of work" or "work items". These are just some division of work into a conceptually unified unit. In general, any work item can be further divided into smaller units of work. Work items are represented by "tickets" or "issues" that track the task, e.g., GitHub issues.
We considered 3 different approaches to prioritization:
- Action Priority Matrix: We score each work item based on the expected effort it will require to complete and the anticipated impact of the results. We then place these tasks on a matrix and coordinate the scores to optimize for the highest value delivery with the least effort.
- Cost of Delay (CoD): Similar to the action priority matrix, this is based on assigning two scores to work items: value and urgency. These scores are then correlated to minimize the negatives financial impacts of delays. It basically works by asking "What is the (financial) impact of this not being completed today?"
- Voting: Finally, we discussed a more subjective strategy based on having people vote on tasks they think are more important and using that as a basis for prioritizing.
More information on various approaches to prioritization can be found in these sources we consulted:
We felt that the CoD approach was too dependent on the need to determine short-term financial returns. This is hard to square with our role as an open source, R&D center serving Informal Systems and the aims of correct software development in the community at large.
We felt that the unstructured voting approach was too subjective. Moreover, while it would work to surface our individual preferences, it doesn't help establish a common ground for shared understanding about priorities.
We finally decided to adopt the Action Priority Matrix. We feel that the process is light-weight enough that we can implement it without slowing down our development but rigorous enough to root our shared understanding in the objective needs and constraints we face in our work.
We follow an adapted version of the approach to APM described in the CIO Wiki.
APM leads us to divide work items into four categories, as follows:
|Impact \ Effort||Low Effort||High Effort|
|High Impact||"Quick Wins"||"Major Projects"|
|Low Impact||"Fill-ins"||"Thankless tasks"|
The category within which a work item falls determines the general approach taken towards the work:
|Quick wins||Do ASAP|
|Major projects||Sustain long term focus|
|Fill-ins||Do in spare time, but never taking time from above|
|Thankless tasks||Avoid, unless there's literally nothing else to do|
We determine which category a work item falls under based on the impact and effort scores assigned to the work. We therefore need a shared understanding of how to assess the impact and effort of a work item. We register only 3 levels on each axis to keep the cognitive load of reckoning scores minimal.
Scores are recorded by affixing labels to the github issue tracking the work item.
Effort is scored best on a rough estimate of the amount of focused time it would take to complete a work item:
|Easy||Can be completed within about 1 day|
|Medium||Can be completed within 3 days|
|Difficult||Will take 5 or more days|
Ideally, as soon as we recognized that an actively planned ticket will take more than 5 days of focused work, we would factor it into smaller tickets, allowing us to avoid perpetually prolonged monster tickets. But some people may prefer to track "major projects" with a single issue rather than a milestone, and this doesn't pose a significant problem.
Impact is scored based on considering impact in the follow 4 domains:
- User / customer: The benefit of the results of a work item to our users and customers
- Mission: Furtherance of our organization's mission and objectives
- Invention: Advancement of state of the art in formal verification and specification
- Development: Improvements to our development capacities and bandwidth (which supports advancing the other three factors).
Here are the meaning of the impact levels, as related to each domains:
- User / customer: Unblocks critical work
- Mission: Advances critical organizational objectives
- Invention: Opens up novel verification and specifications abilities
- Development: Saves > 3 hours per week
- User / customer: Unblocks non-critical work
- Mission: Advances non-critical organizational objectives
- Invention: Makes incremental improvement to verification and specification abilities
- Development: Saves between 1 to 3 hours per week
- User / customer: Improves functionality, but an easy workaround exists
- Mission: No significant advance of organizational objectives
- Invention: No significant improvement to verification and specification abilities
- Development: Saves < 1 hours per week
These are the labels to use on issues:
The initial priority of a requirement should be established at the time work is agreed upon, including when setting plans quarterly and when triaging unplanned work. All collaborators with a stake in the work are responsible for ensuring the work is scored in a way that they feel to be correct.
When unplanned work is introduced, the stakeholders involved should determine its score (using informal language, when needed), and this should be used to decided whether it is worth interrupting any ongoing or planned work.
When deciding which work item to take on next, we should favor work that is
nearest to scoring minimum effort and maximum impact: (
impact-high). Ties should be resolved based on the worker's inclination or
discussions within other stakeholders.
The priority of work should be re-evaluated as the situation changes. E.g.:
- When goals change, then impact should be reconsidered.
- If we discover work was incorrectly scoped, then the effort should be reevaluted.
We can generate views into the 4 quadrants via filters in our project board, or any other tooling or visualization we find suitable.
When reviewing work in progress or queued up next at our weekly meetings, we should always be sure that the highest priority work on the board is being addressed. We should also take this time to estimate priorities for anything new that came up on the week before that hasn't been prioritized already.