A relationship has two roles associated with it. They define the role of one table in association with the other. It is possible to assign more than one relationship between two tables using different roles. Each relationship creates migrated keys from the parent to the child table. Column A table contains columns which are tagged attributes.
Columns can contain data, when they are instantiated as a row.
The column can be either persistent or computed. Computed columns are defined by an expression. Persistent columns can be tagged as primary key columns, nullable columns, and unique columns. They can also contain a default value. Constraints can be checked for any column.