AW: H.450 - "Loose" specification of SyntaxList in X.681?

Horvath Ernst ernst.horvath at SIEMENS.AT
Thu Apr 19 06:26:42 EDT 2001


the syntax for a given object class (e.g. OPERATION) is not loose. It must
be exactly as specified in the definition of the object class after the key
words "WITH SYNTAX".

For the purposes of H.450, the two object classes OPERATION and ERROR are
imported from X.880. All operations and error values are specified using the
syntax of X.880 (alternatively the "raw" form could be used when specifying
an operation or error, but this has not been done in any H.450
recommendation). Your example with commas is no valid syntax according to


> -----Ursprüngliche Nachricht-----
> Von: Frank Derks [mailto:frank.derks at PHILIPS.COM]
> Gesendet am: Donnerstag, 19. April 2001 11:09
> An: ITU-SG16 at mailbag.cps.INTEL.COM
> Betreff: H.450 - "Loose" specification of SyntaxList in X.681?
> Dear experts,
> since H.450 heavily relies on Information Object Classes and since
> the H.450 supplementary services use the user-friendly syntax, I
> have a question relating to the syntax of the specification of this
> syntax.
> X.681 defines SyntaxList as:
> SyntaxList ::= "{" TokenOrGroupSpec empty + "}"
> Other definitions from X.681, that "complete" this specification,
> are:
>   TokenOrGroupSpec ::= RequiredToken | OptionalGroup
>   OptionalGroup ::= "[" TokenOrGroupSpec empty + "]"
>   RequiredToken ::=     Literal |       PrimitiveFieldName
>   Literal ::= word | ","
> For "required" fields from the class, the "syntax list" would
> usually contain phrases consisting of some uppercase description
> consisting of one or more words (separated by spaces),followed by
> one of the fields from the class, etc.
> Obviously, this is covered by the above BNF of X.681, but (as an
> example) "RETURN ,, &ResultType RESULT" would be just as valid as
> "RETURN RESULT &ResultType" with this definition.
> Do I interpret the BNF wrongly, or is this indeed the case?
> Regards,
> Frank
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