Each Change has a single User who is responsible for that Change. Most Builds have a set of Changes: the Build represents the first time these Changes have been built and tested by the Buildbot. The build has a “blamelist” that consists of a simple union of the Users responsible for all the Build's Changes.
The Build provides (through the IBuildStatus interface) a list of Users who are “involved” in the build. For now this is equal to the blamelist, but in the future it will be expanded to include a “build sheriff” (a person who is “on duty” at that time and responsible for watching over all builds that occur during their shift), as well as per-module owners who simply want to keep watch over their domain (chosen by subdirectory or a regexp matched against the filenames pulled out of the Changes). The Involved Users are those who probably have an interest in the results of any given build.
In the future, Buildbot will acquire the concept of “Problems”, which last longer than builds and have beginnings and ends. For example, a test case which passed in one build and then failed in the next is a Problem. The Problem lasts until the test case starts passing again, at which point the Problem is said to be “resolved”.
If there appears to be a code change that went into the tree at the same time as the test started failing, that Change is marked as being resposible for the Problem, and the user who made the change is added to the Problem's “Guilty” list. In addition to this user, there may be others who share responsibility for the Problem (module owners, sponsoring developers). In addition to the Responsible Users, there may be a set of Interested Users, who take an interest in the fate of the Problem.
Problems therefore have sets of Users who may want to be kept aware of the condition of the problem as it changes over time. If configured, the Buildbot can pester everyone on the Responsible list with increasing harshness until the problem is resolved, with the most harshness reserved for the Guilty parties themselves. The Interested Users may merely be told when the problem starts and stops, as they are not actually responsible for fixing anything.