We do not agree that slice names should be unrestricted. The FHIR specification itself specifies rules for slice names in eld-16 . In addition to the rules specified by FHIR, FHIR Shorthand cannot support slice names with [ or ] characters since those characters are critical to specifying slice names in FSH paths. Specification : We will document requirements for slice names in the FSH specification, with reference to FHIR core's constraints. We will also prohibit " [" and "] " in slice names. Implementation : We will also attempt to update the ANTLR grammar to allow the use of FSH keywords as slice names. The ANTLR grammar, however, is considered to be informal – so any remaining issues in the grammar should be interpreted as limitations of the implementation, not formal requirements of the specification. We will include comments in the grammar documenting any gap between the specification and the implementation.