Definition
A stakeholder × activity table with cells containing legend x / p / o / cc; blanks mean 'explicitly judged as no interaction', not omissions.
In detail
The communication matrix governs who attends which meetings, who receives minutes, and via which channel. Legend: x = full attendance and receives minutes, p = partial attendance and receives minutes, o = optional, minutes at own discretion, cc = optional but must receive minutes, blank = explicitly judged as no interaction. The original also provides pros and cons for six communication channels and reminds not to default to the same method for all purposes, and to watch for reluctant stakeholders. It is not a RACI: responsibility assignment has a separate table.
Example in practice
At project initiation, the team lists the sponsor, project owner, client-side project manager, and three team members. Activities are weekly meetings, gate reviews, monthly steering meetings, and minutes. Sponsor: weekly meeting o, gate review x, minutes cc. Client-side finance has an entire blank row and is marked as a reluctant stakeholder; the system prompts to confirm that this is a judgment, not an omission.