if-and-only-if operation

基本解释

The process contains a receive activity followed by an invoke activity, and a reply activity that is needed only if the operation offered by the process is a two-way operation.
代理流程包含一个接收活动，后面跟着一个调用活动，以及一个仅当该流程提供的操作是双向操作时才需要的应答活动。
If the client invokes a web service with the IN-ONLY operation, then the sequence of invocations in both RM Source and RM Destination will be subsets of the sequences, as shown in Figure 7 above.
如果客户机使用 IN-ONLY 操作调用 Web 服务，则 RM Source 和 RM Destination 中的调用序列都将为图 7 中所示的序列的子集。