JBoss.org Community Documentation
In traditional ACID transaction systems, transactions are short lived, resources (such as databases) are locked for the duration of the transaction and participants have a high degree of trust with each other. With the advent of the Internet and Web services, the scenario that is now emerging requires involvement of participants unknown to each other in distributed transactions. These transactions have the following characteristics:
Transactions may be of a long duration, sometimes lasting hours, days, or more.
Participants may not allow their resources to be locked for long durations.
The communication infrastructure between participants may not be reliable.
Some of the ACID properties of traditional transactions are not mandatory.
A transaction may succeed even if only some of the participants choose to confirm and others cancel.
All participants may choose to have their own coordinator (Transaction Manager), because of lack of trust.
All activities are logged.
Transactions that have to be rolled back have the concept of compensation.