Re: Error definition

Right, so “bad.ixml” should only cause an error if we’re providing it as an input grammar and “something_else.ixml” as an input string. Which, I guess, implies that providing an unrecognizable input string is only an error in a secondary sense - i.e. when the input string was originally provided as an ixml input grammar, and is being parsed against the ixml specification grammar in order to fulfil that role. So it makes sense to say, not that it’s an error because the input string is unrecognizable, but because the ixml input grammar is not, in fact, an ixml grammar.

Thanks for your patience, everyone. That’s clarified some things for me (even if the paragraph above doesn’t actually exude clarity!).

BTW
___________________________________________________ 
Dr. Bethan Tovey-Walsh 
Myfyrwraig PhD | PhD Student CorCenCC 
Prifysgol Abertawe | Swansea University 
Croeso i chi ysgrifennu ataf yn y Gymraeg.

> On 5 Feb 2022, at 13:55, C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com> wrote:
> 
> 
> Bethan Tovey-Walsh writes:
> 
>> Okay, that’s all fair. ...
>> ... My only slight disagreement is that, if we’re talking
>> specifically of an ixml grammar parser, failure to recognise the input
>> must be an error. If the input string isn’t recognised, it isn’t a
>> valid ixml grammar and it can’t subsequently be used as the “ixml
>> grammar” input to an ixml input parser.
> 
>> Does that make sense?
> 
> I think it does.  (And I think the reasons that 'error' makes sense here
> and not in the case of the input string not being a sentence are (1)
> that the ixml spec does define conformance rules for input grammars, and
> (2) that a user who specifies an input grammar is implicitly warranting
> that it's a conforming gramar.
> 
> Note that I think point (2) has a slighty subtle consequence.  It means,
> I think, that if the file "bad.ixml" contains the non-grammar
> 
>   S ::= "hi mom".
> 
> then whether it is "in error" in the narrow sense seems to depend on how
> the processor is invoked. If I invoke an ixml processor asking to parse
> the input "hey, bro!" against the grammar in bad.ixml, the processor
> will discover that bad.ixml is not a conforming grammar, and it seems to
> me to make sense tosa that it is "in error".
> 
> If on the other hand I invoke the ixml processor asking it to parse
> bad.ixml against the ixml specification grammar, I am making no implicit
> claims that bad.ixml is a conforming grammar and so I would be
> uncomfortable saying that in that case the file bad.ixml is "in error".
> 
> Michael
> 
> -- 
> C. M. Sperberg-McQueen
> Black Mesa Technologies LLC
> http://blackmesatech.com
>