anchor.diff:  	Name = {"name", "PublicWLANAccessUsageSpec"},
   	Desc = {"description", "Specification for IPDR Public WLAN Access - WISP Use Case"},
   	Start = {"startDateTime", "2017-01-01T00:00:00Z"},
  -	End = {"endDateTime", "2017-12-31T23:59:59Z"},
  +	End = {"endDateTime", undefined},
   	Valid = {"validFor", {struct, [Start, End]}},
   	Chars = lists:reverse(spec_public_wlan1([])),
   	Char = {"usageSpecCharacteristic", {array, Chars}},
  
positive.code: 	Name = {"name", "AAAAccountingUsageSpec"},
  	Desc = {"description", "Specification for SigScale OCS accounting requests."},
  	Start = {"startDateTime", "2017-01-01T00:00:00Z"},
  	End = {"endDateTime", "2017-12-31T23:59:59Z"},
  	Valid = {"validFor", {struct, [Start, End]}},
  	Chars = [spec_protocol(), spec_node(), spec_server_address(),
  			spec_server_port(), spec_type_accounting(),
  
negative.code: 	Name = {"name", "VoIPUsageSpec"},
  	Desc = {"description", ""},
  	Start = {"startDateTime", "2018-03-12T00:00:00Z"},
  	End = {"endDateTime", undefined},
  	Valid = {"validFor", {struct, [Start, End]}},
  	Chars = lists:reverse(spec_voip1([])),
  	Char = {"usageSpecCharacteristic", {array, Chars}},
  