Pass/Propagate data from a parent case to child case

Sometime in a case management application where we have one or more subcases for a case, we may need to use some data from a parent case in a child case. e.g. In a 'Request Purchase' case we have one Purchase Order subcase where in the subcase we may need OrderId or PurchaseId from the case. This is called 'Data Propagation'. 
To propagate the data from a case to subcase we need to configure the data propagation on the parent case. The data propagation configuration is available on Details tab of a parent case. Click edit to configure data propagation.
Here we have two options to map the data:-
a. Directly map properties of parent case to the properties of child case
b. Use a data transform

Normally we map the properties but if you need some conditional mapping or more advanced data propagation then you go with data transform. 

Important:- Data Propagation only happens once i.e. when cases are initially created. If you propagate a property from the Parent case to a child case, and the property value later changes on the Parent Case, the property on the child case does not get updated.