Subject: [Megaco] Ambiguous definition of auditReturnParameter in v2 ABNF

From: Micael Karlberg <[email-masked]>
Date: Thu, 17 Jul 2003 11:31:34 +0200

Hi,

The 'auditReturnParameter' appears to be ambiguously defined in version 2
of the ABNF.

An example. If the 'auditReturnParameter' contains the following 
sequence of tokens:

   "EB { hobbes }"

i.e.

    EventBufferToken LBRKT pkgdName RBRKT

then it may be an 'auditItem' (see 'indAudeventBufferDescriptor') or an 
'eventBufferDescriptor'

What is the intention here? Should this sequence of tokens be
interpreted as an 'auditItem' or an 'eventBufferDescriptor?

As a parser implementor I need a well defined, unambiguous grammar to
rely on.

The grammar looks like this (a little bit simplified):

  auditReturnParameter        = eventBufferDescriptor / auditItem

  eventBufferDescriptor       = EventBufferToken 
                                [ LBRKT eventSpec *(COMMA eventSpec) RBRKT]

  eventSpec                   = pkgdName  
                                [ LBRKT eventSpecParameter 
                                        *(COMMA eventSpecParameter) RBRKT]

  auditItem                   = indAudterminationAudit 

  indAudterminationAudit      = indAudauditReturnParameter
                                *(COMMA insAudauditReturnParameter)

  indAudauditReturnParameter  = indAudeventBufferDescriptor

  indAudeventBufferDescriptor = EventBufferToken LBRKT indAudeventSpec RBRKT

  indAudeventSpec             = pkgdName 
                                [ LBRKT indAudeventSpecParameter RBRKT ]

Regards,
	/BMK

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