A role is an entity (a person, computer, or any other type of actor) or groupofentities that have the same rights and obligations with respect to performing a task or a groupof tasks.
Each of the entities in a message group is an entire message.
消息组中的每个实体都是一个完整的消息。
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Business domains represent some particular and often tightly inter-related groupof business entities that collaboratively work together to fulfill some business functionality.