实体框架如何判断关系中是否应该使用多个“一”或“零或一”？

I'm programmatically creating an edmx file as part of our code generation process and I'd like to know how the designer decides to use "1" or "0..1" for a relationship when you "Update model from database". Any insight on this? ThanksI'm programmatically creating an edmx file as p