You can define record tags for Business Objects and Business Object Types in System Administration Applications -> Database Administration.

Business Object Relationship Management Window Opening Parameters

Related Object

To associate a business object BO1 with another business object (BO2), you must first select "Yes" from the drop-down box.

Source Code

After writing the source code, if you click the "Relationships" button on the business object (BO1) and then the "New Business Object Relationship" button, you can add the "Related Object" (BO2) by selecting it from the drop-down box and the "Object ID" by selecting it from the window.