The separation unit comprises a plurality of buffering elements and at least one extensiblemember which is suitable for extending along at least one direction.
分隔单元包括多个缓 冲件以及至少一个伸缩件，其适于沿至少一个方向伸缩。
2
What makes this example extensible is that the schema developer only has to add a new element declaration indicating that it is a member of the substitution group.