Minor (related to: ODATA-53)
The current specification for the Edm:UnderlyingType attribute reads as follows:
"An enumeration type has an underlying type which specifies the allowable values for member mapping. The enumeration type MUST assign an value of Edm.Byte, Edm.SByte, Edm.Int16, Edm.Int32, or Edm.Int64 to the edm:UnderlyingType attribute. If the underlying type is not specified, a 32-bit integer MUST be used as the underlying type."
edm:UnderlyingTYpe attribute should be optional, as implied by the third sentence, so the "MUST" in the second sentence should be changed to "MAY".
Also, the text reads a bit strange after application of ODATA-53 ("...MUST assign an value"), and the enumeration type doesn't assign a value, the edm:UnderlyingType attribute MAY BE assigned a value.
Suggest rewording as per proposal.