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Re: parser validation tools

• Subject: Re: parser validation tools
• From: Nick Spadaccini <nick@xxxxxxxxxxxxx>
• Date: Tue, 16 May 2000 17:53:47 +0100 (BST)

On Tue, 16 May 2000, Richard G. Ball wrote:

> Brian, is the absence of a dataitem an error or does the dataname just get
> associated with a value of "undefined"?

Terminaology first. A dataitem is a tuple, consisting of a dataname and
the associated datavalue. In essence it is not possible for a dataitem to
be absent. If a dataname does not have an associated datavalue then this
is an ERROR - because it violates the CIF (STAR actually) specification.

The reason why you SHOULDN'T think of this case as "undefined" is because
undefined in the STAR format has meaning. Namely

_dataname .  # means in this particular case there is no 
             # meaningful value for this dataname.

also a related example is

_dataname ?  # means there is value, I just don't know what it is

So the case of

_dataname   #
_another_dataname #

should raise an exception and be flagged as an invalid CIF.

cheers

Nick

--------------------------------
Dr Nick Spadaccini
Department of Computer Science              voice: +(61 8) 9380 3452
University of Western Australia               fax: +(61 8) 9380 1089
Nedlands, Perth,  WA  6907                 email: nick@cs.uwa.edu.au
AUSTRALIA                        web: http://www.cs.uwa.edu.au/~nick

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