reference column

基本解释

The elements in the Reference column specialize the elements in the Topic column.
引用列中的元素专门化了主题列中的元素。
Figure 8 shows that the left outer join operations are cascaded if a rule uses more than one reference column.
图 8 展示了如果规则使用了多个参考列，那么左外部连接就进行级联。
A rule uses a reference column when it contains either an in_reference_column test or a lookup (value, refKey, refValue) function.
当规则包含 in_reference_column 测试或者 lookup (value, refKey, refValue) 函数时，采用参考列。