Define Slices

To further customize a base Resource you can slice available elements to capture a variety of the same element. This is particularly helpful when you want to capture multiple versions of an element of your base Resource. For instance multiple patient identifiers or multiple name parts. This allows you to define specifics such as CodeableConcepts for each part of the sliced object. This process entails slicing a structure element into sub items. The sub items that are created are then referred to as slices.

Slicing in Forge

Select the element that you want to slice and click on Slice.

Slicing an element in Forge

The element is now ‘Sliced’ and it is possible to add slices by clicking Add Slice. You can create as many slices as necessary by selecting the sliced element and clicking Add Slice again. The added slices can be defined and constrained as any other element.


After adding slices, Forge shows a validation message containing the message that there is no discriminator defined for the sliced elements.

Slicing an element in Forge

The discriminator is used to distinguish the sliced elements from one another. The discriminators in their sum should allow applications to easily determine which slice belong to each section. The discriminator information can be provided in the Element Properties of the sliced element under Slicing Details.

Slicing an element in Forge

More information concerning slicing and discriminators can be found here:

Type Slicing

Type slicing applies to so-called polymorphic “choice type” elements that support multiple data types. A choice type element has a name that ends with “[x]”, e.g. Observation.value[x]. Using type slicing, you can define constraints for specific element types. Per definition, the slicing discriminator of a type slice is equal to “@type”. Each slice constraint you define must have a unique type.