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Slicing is a nice idea for defining complex or composite data elements used by several FHIR ressources.

"Within a structure definition, a slice is defined using multiple element entries that share a path but have distinct names. These entries together form a "slice group" with useful featured described in http://www.hl7.org/fhir/2015May/profiling.html.

However in the FHIR ressource "DataElement" itself the use of slicing within the ElementDefinition ist not allowed: see https://www.hl7.org/fhir/dataelement.html

=> Definition of element, No base allowed, No slicing allowed

What is the reason for not allowing slicing within DataElements?

Josef Ingenerf
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The purpose of DataElement is to define elements. All data elements defined are stand-alone - they don't inherit from other data elements. As such, there seemed to be no place/utility for slicing. (It exists on DataElement from its use in StructureDefinition.) Do you have a use-case for slicing when defining DataElements?

Lloyd McKenzie
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  • Thank you for your answer. Yes, data elements defined are stand-alone. However we not only have "atomar" data elements with just one element definition like "age". Often it is very useful to build complex data elements like the famous "blood pressure" with two interconnected element definitions "systolic bp" and "diastolic bp." There are a lot of use cases for those complex data elements on their own; i.e. to reuse them in other applications. – Josef Ingenerf Nov 26 '15 at 14:13
  • Complex data elements are possible (just as complex resources are possible), but this doesn't involve slicing. Slicing is always about constraining a parent model and DataElements have no notion of constraint. – Lloyd McKenzie Nov 26 '15 at 18:44
  • Ok, once we have fully understood the mechanism slicing, it makes sense not to use it in the standalone Fhir Resource Data Element. – Josef Ingenerf Dec 08 '15 at 18:11