For foreign key creation, another table with a primary key with a compatible datatype is required.
对于创建外键，则需要另外一个具有主键的表，且该主键具有兼容的数据类型。
2
The key to modeling this type of relational data in XML is to understand all the tools you have at your disposal, and apply common sense to determine what will work best in a particular case.
在 XML 中建模这种类型的关系数据的关键是要了解您有可使用的所有工具，并应用常识来确定什么工具最适合某种特定情况。
3
For each data element, LOM specifies a name, explanation, size, example value, datatype, and other key details.