The relationship between elements in the XML hierarchy defines the relationship between XML views in a PowerCenter definition. In a source definition, a view does not have to be related to any other view. Therefore, views in a source definition do not require primary or foreign keys. A denormalized view can be independent of any other view. However, the Designer generates keys if you do not designate key columns when views are related to other views.

Each view in a target definition must be related to at least one other group. Therefore, each view needs at least one key to establish its relationship with another view. If you do not designate the keys, the Designer generates primary and foreign keys in the target views. You can define primary and foreign keys for views if you create the views and relationships in the XML Editor instead of allowing the Designer to create them for you.

When the Designer creates a primary or foreign key column, it assigns a column name with a prefix. In an XML definition, the prefixes are XPK_ for a generated primary key column and XFK_ for a generated foreign key column. The Designer uses the prefix FK_ for a foreign key that points to a primary key.

For example, when the Designer creates a primary key column for the Sales group, the Designer names the column XPK_Sales. When the Designer creates a foreign key column connecting a sales group to another group, it names the column XFK_Sales. You can rename any column name that the Designer creates.

If a mapping contains an XML source, the Integration Service creates the values for the generated primary key columns in the source definition when you run the session. You can configure start values for the generated keys.