Associated with every transaction is a coordinator, which is responsible for governing the outcome of the transaction. The coordinator may be implemented as a separate service or may be co-located with the user for improved performance. Each coordinator is created by the transaction manager service, which is in effect a factory for those coordinators.
A coordinator communicates with enrolled participants to inform them of the desired termination requirements, i.e., whether they should accept (e.g., confirm) or reject (e.g., cancel) the work done within the scope of the given transaction. For example, whether to purchase the (provisionally reserved) flight tickets for the user or to release them. An application/client may wish to terminate a transaction in a number of different ways (e.g., confirm or cancel). However, although the coordinator will attempt to terminate in a manner consistent with that desired by the client, it is ultimately the interactions between the coordinator and the participants that will determine the actual final outcome.
A transaction manager is typically responsible for managing coordinators for many transactions. The initiator of the transaction (e.g., the client) communicates with a transaction manager and asks it to start a new transaction and associate a coordinator with the transaction. Once created, the context can be propagated to Web services in order for them to associate their work with the transaction.