remove reference to event messages from ABNF expressions

versions/1.0.0.md

@@ -820,12 +820,12 @@ This object MAY be extended with [Specification Extensions](#specification-exten
 
 
 ### Runtime Expressions
-A runtime expression allows values to be defined based on information that will be available within an HTTP message, an event message, and within objects serialized from the Arazzo document such as [workflows](#workflow-object) or [steps](#step-object).
+A runtime expression allows values to be defined based on information that will be available within the HTTP message in an actual API call, or within objects serialized from the Arazzo document such as [workflows](#workflow-object) or [steps](#step-object).
 
 The runtime expression is defined by the following [ABNF](https://tools.ietf.org/html/rfc5234) syntax:
 
 ```abnf
-      expression = ( "$url" / "$method" / "$statusCode" / "$request." source / "$response." source / "$message." source / "$inputs." name / "$outputs." name / "$steps." name / "$workflows." name / "$sourceDescriptions." name / "$components." name / "$components.parameters." parameter-name)
+      expression = ( "$url" / "$method" / "$statusCode" / "$request." source / "$response." source / "$inputs." name / "$outputs." name / "$steps." name / "$workflows." name / "$sourceDescriptions." name / "$components." name / "$components.parameters." parameter-name)
       parameter-name = name ; Reuses 'name' rule for parameter names
       source = ( header-reference / query-reference / path-reference / body-reference )
       header-reference = "header." token