The mapping table also allows the user to convert source types to target types, or defineconstant mappings that set constant values to items in the target schema.
映射表还允许用户将源类型转化成目标类型，或定义常量映射 来将常量设置为目标架构中的项目。
2
So we define, then, equilibrium constant this way.
所以我们这样定义平衡常数。
3
My favorite is to use a configuration file and define a constant in it that holds the format string for the date function.