在使用UML建模时，序列图展现了一组对象和由这组对象收发的消息，其特点是()。

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Microsoft's COM is a software(71) that allows applications to be built from binary software components. COM is the underlying architecture that forms the foundation for higher-level software services, like those provided by OLE. COM defines a binary standard for function calling between components, a way for components to dynamically discover the interfaces implemented by other components, and a mechanism to identify components and their interfaces uniquely.

 OLE is a compound(72) standard developed by Microsoft. OLE makes it possible to create(73) with one application and link or embed them in a second application. Embedded objects retain their original format and(74) to the application that created them. Support for OLE is built into the Windows and MacOS Operating Systems. A(75) compound document standard developed mainly by Apple and IBM is called OpenDoc.

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某商场的部门、员工和商品3个实体之间的关系如图5-7所示。假设每个部门有若干名员工，每种商品只能由一个部门负责销售。如果用户要求得到如表5-7所示的结果，则需要(52)，并增加关系模式(53)。如果要求查询某部门负责销售的商品，则需要(54)。

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