Key responsibility roles
ResponsibleThose who do the work to achieve the task. There is at least one role with a participation type of responsible, although others can be delegated to assist in the work required (see alsoRASCI below for separately identifying those who participate in a supporting role).
Accountable (also approver or final approving authority)The one ultimately answerable for the correct and thorough completion of the deliverable or task, and the one who delegates the work to those responsible.  In other words, an accountablemust sign off (approve) on work that responsible provides. There must be only one accountable specified for each task or deliverable.
InformedThose who are kept up-to-date on progress, often only on completion of the task or deliverable; and with whom there is just one-way communication.
Very often the role that is accountable for a task or deliverable may also be responsible for completing it (indicated on the matrix by the task or deliverable having a role accountable for it, but no role responsible for its completion, i.e. it is implied). Outside of this exception, it is generally recommended that each role in the project or process for each task receive, at most, just one of the participation types. Where more than one participation type is shown, this generally implies that participation has not yet been fully resolved, which can impede the value of this technique in clarifying the participation of each role on each task.
There is a distinction between a role and individually identified people: a role is a descriptor of an associated set of tasks; may be performed by many people; and one person can perform many roles. For example, an organisation may have ten people who can perform the role of project manager, although traditionally each project only has one project manager at any one time; and a person who is able to perform the role of project manager may also be able to perform the role of business analyst and tester.