Creating a Link

What is a Link?

Links are the core business relationship, that is a combination of business keys from the related core business entities.
The standard Link is defined by the business key attributes of two or more related Hubs with a foreign key join.
It is generally defined with a field for the load timestamp (load date) and a field for where the data came from (record source).
Optionally it can be defined with a surrogate attribute by either an auto-incremented integer or a hash of the Hub attributes; the business key attributes are generally removed in this scenario.

How to create a Link in 3D?

1. Create an entity for the core business relationship; for example, Customer_Orders.
2. Identify the Hub entities the Link will create relationships between; for example, Customer and Orders.
3. Make copies of the business attributes in these entities into the new entity.
4. Set the attribute types on these attributes as "Link business key".
5. Create the foreign key joins between the newly created attributes and the attributes in the related Hubs. Make sure the foreign key constraint name is set if the attributes in the Hub are compound / composite.
6. Create a source set (or use an empty one) with a name associated to the source system (for documentation).
7. Choose the source entity that defines the Link and create at least an entity level source mapping. The source attributes can be defined in several ways:
   
   1. If the foreign key attribute in the Link is the related Hub business key, use that.
   2. If the related Hub business key is the natural key and not part of the foreign key join, add the Hub's source entity and choose the same source attributes in the Hub.
8. Repeat step 6 and 7 for any additional source systems.

Example