Models are used in many ways: to predict system qualities, reason about specific properties when aspects of the system are changed, and communicate key system characteristics to various stakeholders.
模型被用在很多的方面：预期系统的质量，当系统的某些方面变化时推理特定的属性，和为各种涉众沟通关键的系统特征。
However ElectricityDeal had too many of its own properties. Accordingly many electricity-specific nullable columns were added to the Deal table.
但是ElectricityDeal有太多自己的属性，因此有很多电相关的可空字段加入了Deal表。
Today, they are still commonly used in many cultures for general health care and specific therapeutic properties .
这种具有保健及特殊医疗特性的治疗方式在现今仍然持续被使用。
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