But the traditional PBXs are based on private technology and lacks of open standards, have shortages in flexibility and extensibility, needs high cost for maintenance and upgrade.

然而传统PBX采用的是专用技术，缺乏技术标准，可扩展性和灵活性差，维护成本和升级费用高昂。

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This brittle aspect of existing systems is in part responsible for the high cost of system maintenance and the limitations around the number of trading partners one can manage.

现有系统的这个缺点是造成系统维护费用高和可管理的合作伙伴的数量受到限制的原因的一部分。

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The cost for storage and maintenance of a functional index can be high.

函数索引的存储和维护成本较高。

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