Bossa reference manual

Abstractions

A Bossa project has one or more applications. A application has a dynamic set of jobs. Each one has an associated set of arguments describing its parameters or input files. Each job has a set of job instances. Each one represents a copy of the job, either in progress or completed. Each job instance is assigned either to a user or to a team.

Applications are classified as:

• Online: jobs are performed by a single user, sequentially, in a web browser.
• Offline: jobs are not online, e.g. because they're potentially handled by a group of users, or requires other asynchronous activity.

An application has an associated URL identifying a script that takes a job ID argument and displays the job instance. The job may consist of a single web page or a sequence of web pages. In either case the last page in the sequence, when done, should call Bossa API functions to record the completion of the task, and perhaps display another task.

Applications are either:

• Individually validated: the application has a server-side program that examines a completed instance and decides if it's valid.
• Group validated: the application has a server-side program that examines a group of instances, sees if there's a consensus, and if so constructs a canonical result and marks the instances as valid or invalid.

A project can configure:

• A maximum number of outstanding offline jobs per user or group
• A maximum number of jobs per day issued per user or group

Volunteer characteristics

For each application and each user, Bossa maintains skill estimate, an estimate of the user's skill at that task. This is maintained in the user's database record. Normally it's a single number in [0..1], and it's initially zero.

The skill estimate can be computed in any of several ways:

• The results of the user's interaction with a Bolt course associated with the application.
• The user's performance on "calibration jobs" mixed into the stream.
• The fraction of the user's results classified as invalid by redundancy.

Skill estimates are used for two purposes:

• To decide whether to give jobs to a user;
• To decide how many redundant instances of a given job are needed.

Implementation

To get work, a user goes to a particular Bossa-supplied page. There he sees a list of applications for which tasks are available and for which he is qualified, and links to courses for other applications. Online and offline applications are listed separately. Each application has an estimate of the time or other resources required to complete a job.

Selecting an online application invokes the Bossa scheduler script, which selects a job instance suitable for the user, and redirects to its instance URL.

Selecting an offline application invokes the Bossa scheduler, which selects a job and redirects to its instance-start URL.

Team administrators are provided with an interface for getting offline jobs for the team. The scheduler allows a team to get instances only for applications for which some team member has the required skill.

Users and teams are provided with an interface for seeing a list of pending offline jobs. They can indicate that one of them is completed; this takes them to the instance-complete URL for that job.

Integration with BOINC

Some offline jobs may involve computation done through BOINC; i.e. if the job is assigned to a team, the computation is queued in the project's BOINC server and dispatched to members of the team. (Or if the job is assigned to a user with many computers, those computers are used).