Customizing the metamodel : Keywords for USRPROPS : BY
  
BY
An often used keyword used as shown in the following expressions: DEFINED BY, RELATED BY, RELATE BY, and KEYED BY. For more information, refer to the specific keyword combination.
Example
DEFINITION "Column"
{..
PROPERTY "Database Name"
{ KEY EDIT OneOf "Database" RELATE BY "nothing" }
..
}