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RE: Confidence property

From: Young, Milan <Milan.Young@nuance.com>
Date: Fri, 15 Jun 2012 20:05:33 +0000
To: Glen Shires <gshires@google.com>
CC: "public-speech-api@w3.org" <public-speech-api@w3.org>
Message-ID: <B236B24082A4094A85003E8FFB8DDC3C1A47385D@SOM-EXCH04.nuance.com>
Glen and I don't appear to be converging on a solution and I believe it's time to turn to the community for help.  Rather than plunge into the details of the proposals, I'd like to invite all interested parties to start by voting A/B on this short questionnaire:

Question-1) You are a web developer and set a confidence threshold to .75.  Would you prefer:

A)      Results will be returned only if the confidence is >= to .75.  All nomatch events that contain confidence scores are guaranteed to be < .75.

B)      Results of various confidence are returned (i.e. no direct correlation to the specified threshold).  Nomatch events also lack correlation (eg a score of .9) could occur.

Question-2) You are a web developer in class 2 (intelligent, motivated, but lacks speech science background).  You are currently using a confidence value of .5 on a mobile application, but too many results are being returned which is causing latency.  You want to improve the performance of your system and by limiting the number of results.  You start by looking at the list of results and try to find an inflection point between reasonable and unreasonable values.  Perhaps running a few informal trials with a live microphone.  You now need to choose the new threshold.  Which methodology seems easier?

A)      Specify a threshold just below the inflection point.

B)      Add .1 to the threshold, run all your trials again looking to see if unreasonable values were returned, add another .1 to the threshold, repeat.

Quesiton-3) You are part of the team authoring a new specification for a HTML/Speech marriage (think hard :)).  It's come time to write the text for how confidence thresholds affect results.  Which design seems like the best way to promote a uniform experience across UAs and engines:

A)      Require engines to report results on the same scale as the developer-specified threshold.  If the engine knows that 0.5, for example, does not provide meaningful results for a particular dialog type, they should either fix that problem or risk users/developers going elsewhere.

B)      Specify that there is only a casual correlation between thresholds and scores in the results.  Some engines might provide a consistent scale, some engines may use various skews and choose not to map back onto the threshold scale.


From: Glen Shires [mailto:gshires@google.com]
Sent: Friday, June 15, 2012 12:00 PM
To: Young, Milan
Cc: public-speech-api@w3.org
Subject: Re: Confidence property

It may be that we have a misunderstanding in how we both define "native confidence values".  I have been using that term, and continue to use that term to indicate a 0.0 - 1.0 scale that has not had any skew applied to make 0.5 reasonable.  I have not been using that term to refer to any internal recognizer scale that is other than 0.0 - 1.0.

Comments inline below...

On Thu, Jun 14, 2012 at 6:04 PM, Young, Milan <Milan.Young@nuance.com<mailto:Milan.Young@nuance.com>> wrote:
You argue that there exists some recognizer that is NOT capable of giving a meaningful native interpretation to thresholds like '0.5'.  I will accept that.
[Glen] Thank you

You further suggest that these same recognizer(s) have some magic ability to transform these thresholds to something that IS meaningful.  I will accept that too.  Let's call that magic transformation webToInternal() and it's inverse internalToWeb().
 [Glen] OK

Without requiring this engine to expose internalToWeb() a developer could set a threshold like "0.5" and get back score like "0.1".  If you were a developer, would that make sense to you?
[Glen] Yes

  What practical use would you even have for such a number?
[Glen] I believe most Group 2 web developers don't care to look at confidence values:

 - Some will simply set nomatchThreshold = 0.5 and control their application based on whether onresult or onnomatch fires.

 - Some more sophisticate Group 2 developers will set nomatchThreshold = 0.5 and may increment it up or down based on if onresult or onnomatch is firing too often or rarely.

 - Only the most sophisticated Group 2 developers will look at the confidence values returned in the results or in emma. Since they are processing them in a recognition-dependent manner, they must only compare relative values. For example, if they find that the second alternative has a confidence value relatively near the first, the app may ask the user to disambiguate.  Using the example you give, if the top result is 0.1 and the second result is 0.085, the app could ask the user to disambiguate.

For Group 3 developers that do process these values, getting back the 0.1 result is invaluable, because it matches the native levels in their tuning tools, logs and other applications.

So yes, this has very practical uses and benefits for Group 2 and Group 3 developers.

It may as well be a Chinese character.
[Glen] Fortunately, it is a float, and can easily be compared against other float values.

Wouldn't it be a lot more useful to developers and consistent with mainstream engines to simply require support for internalToWeb()?  I'm sure folks that are capable of building something as complicated as a recognizer can solve an math equation.  I'll even offer to include my phone number in the spec so that they can call me for help :).
[Glen] No. This would be very problematic for Group 3 developers that use these recognizers. Their tuning tools, their logs, their other applications all may be based on native confidence values, and this complicates their implementation, as you have pointed out. Instead, Group 3 developers would much prefer to only use native values, which they can do because the native values are returned in the results and in emma. Yes, they do have to copy-and-paste a short JavaScript function for this, but that's trivial.  For Group 2 and Group 1 developers, there's no difference whether these recognizers support internalToWeb().

Thank you
Received on Friday, 15 June 2012 20:06:06 UTC

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