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ABNF: "public" does too much

From: jim jackson <jf_jackson@hotmail.com>
Date: Tue, 07 Jan 2003 06:41:50 -0500
To: www-voice@w3.org
Message-ID: <F51S00Pph9XiThHoGAj0001f0e8@hotmail.com>

In Speech Recognition Grammar Specification, "public" means so much that it 
ends up with being very confusing.

In ABNF (and its XML counterpart) a rule with public scope is altogether:
- a rule that can be used from an external grammar--let's call this feature 
- a rule that can be activated and deactivated for speech recognition--let's 
call this "activation";
- a rule that is the top-level syntax of spoken input--let's call it 

The 3 notions are completely different but they are merged into "public" 
which creates problems.

1. top-level is not activation

In http://www.w3.org/TR/speech-grammar/#S3.2 and also in 
http://www.w3.org/TR/speech-grammar/#S4.7, those notions are explicitly 
considered as synonyms, but now look at the following grammar:

root $r;
$r = I want to go to $cities;
$cities = $florida | $california | ...;
public $florida = tampa | miami |...;
public $california = SF | LA | ...;

The only sentences you want to allow start with "I want to go to".
Also you want to activate and deactivate Floridian/Californian cities in 
order to lower perplexity. However you don't want your sentences to be 
limited to bare cities.

This little toy example can have very many different applications in 
telephony or in web browsing (in general you want the activation to apply 
only to a sub-sentence that appears in a carrier phrase, not to the whole 
sentence). It shows there are rules that may be activated while they should 
not be at top-level.

Confusing top-level and activation can be a handicap for some applications.

2. top-level is not export

It is not because you want a rule to be exported that you want it to be at 
top-level as well.
For example say you have a sub-grammar of numbers that you use in several 
applications: it's very unlikely that you wish numbers to be uttered 
alone--outside any carrier phrase.

As a consequence when you import a rule from a grammar G1 into a grammar G2, 
you have at top-level: all sentences at top-level of G2 plus the rule(s) you 
import from G1. This looks very awkward to me.

3. export is not activation

This issue is touched in http://www.w3.org/TR/speech-grammar/#AppI as a 
"Consideration for Future Versions". I fully agree but I consider this less 
of a problem than both the previous ones.


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Received on Tuesday, 7 January 2003 06:42:22 UTC

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