Supporting roles represent roles that must be either informed or consulted by the backlog owner. Customers, stakeholders, and SMEs all may need to be consulted or informed as rocks are refined and the solution emerges. Some of these roles may overlap.
The customer receives or benefits from the solution. They may need to be informed of the decision about precisely what the team will build.
The stakeholder is any individual who, at a minimum, must be consulted about precisely what is being built. Stakeholders may also have decision-making authority regarding the building process. A customer may also be a stakeholder if they need to be consulted regarding decisions about the solution.
Subject Matter Export (SME) is someone with in-depth knowledge of the relevant problem domain, solution technology, or development practices. SMEs use their knowledge to advise other roles about deciding precisely what to build. They are also responsible for providing the expertise other roles may need to perform their jobs.
While SMEs can collaborate with all roles, they typically tend to advise solution owners, analysts, and backlog owners.