Without an identifier, there is no way to represent an entity as metadata.
如果没有标识符，我们就没有办法把这个实体表现为元数据。
2
If it applies to the current transition and entity, the plug-in will undertake the required validation, adding metadata where required.
如果适用于当前的转换和实体，则插件将执行必需的验证，并在所需的地方添加元数据。
3
For better readability, the relationships in our scenario are expressed through object or relational metadata specified directly in the entity class files.