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SpeechInputResult merged proposal

From: Michael Bodell <mbodell@microsoft.com>
Date: Thu, 29 Sep 2011 09:20:50 +0000
To: "public-xg-htmlspeech@w3.org" <public-xg-htmlspeech@w3.org>
Message-ID: <22CD592CCD76414085591204EB19F4E823905341@TK5EX14MBXC262.redmond.corp.microsoft.com>
So we have two existing proposals for SpeechInputResult:

Bjorn's mail of: http://lists.w3.org/Archives/Public/public-xg-htmlspeech/2011Aug/0033.html

Satish's mail of: http://lists.w3.org/Archives/Public/public-xg-htmlspeech/2011Sep/0034.html

I like Bjorn's proposal in that it incorporates the items we talked about at the F2F including:

- EMMA XML representation
- a triple of utterance, confidence, and interpretation
- nbest list

But it doesn't incorporate continuous recognition where you could get multiple recognition results.

Satish's proposal deals with the different prelim, stable, and alternatives by having an array of them and a span of them which gets the continuous part right, but which I fear breaks some of the things we want in the simple non-continuous case (as well as in the continuous case) like the EMMA XML, the interpretation, and simplicity.

What about something that tries to combine both ideas building off Bjorn's proposal but adding the arrays idea from Satish's to handle the continuous case.  Something like:

interface SpeechInputResultEvent : Event {
        readonly attribute SpeechInputResult result;
        readonly attribute short resultIndex;
        readonly attribute SpeechInputResult[] results;
        readonly attribute DOMString sessionId;
    };

interface SpeechInputResult {
   readonly attribute Document resultEMMAXML;
   readonly attribute DOMString resultEMMAText;
   readonly attribute unsigned long length;
   getter SpeechInputResultAlternative item(in unsigned long index);
};
// Item in N-best list
interface SpeechInputAlternative {
   readonly attribute DOMString utterance;
   readonly attribute float confidence;
   readonly attribute any interpretation;
};

It is possible that the results array and/or sessionId belongs as a readonly attribute on the SpeechInputRequest interface instead of on each SpeechInputResultEvent, but I figure it is easiest here.  

If all you are doing is non-continuous recognition you never need look at anything except the result which contains the structure Bjorn proposed.  I think this is a big simplicity win as the easy case really is easy.

If you are doing continuous recognition you get an array of results that builds up over time.  Each time the recogntion occurs you'll get at least one new SpeechInputResultEvent returned and it will have a complete SpeechInputResult structure at some index of the results array (each index gets its own result event, possibly multiple if we are correcting incorrect and/or preliminary results).  The index that this event is filling is given by the resultIndex.  By having an explicit index there the recognizer can correct earlier results, so you may get events with indexes 1, 2, 3, 2, 3, 4, 5, 6, 5, 7, 8 in the case that the recognizer is recognizing a continuous recognition and correcting earlier frames/results as it gets later ones.  Or, in the case, the recognizer is correcting the same one you might go 1, 2, 2, 2, 3, 3, 4, 4, 4, 5 as it gives preliminary recognition results and corrects them soon there after.  If you send a NULL result with an index that can remove that index from the array.

If we really wanted to we could add a readonly hint/flag that indicates if a result is final or not.  But I'm not sure there is any value in forbiding a recognition system from correcting an earlier result in the array if new processing indicates an earlier one would be more correct.

Taking Satish's example of the processing the "testing this example" string and ignoring the details of the EMMA and confidence and interpretation and sessionId you'd get the following (utterance, index, resutls[]) tuples:

Event1: "text", 1, ["text"]

Event2: "test", 1, ["test"]

Event3: "sting", 2, ["test", "sting"]

Event4: "testing", 1, ["testing", "sting"]

Event5: "this", 2, ["testing", "this"]

Event6: "ex", 3, ["testing", "this", "ex"]

Event7: "apple", 4, ["testing", "this", "ex", "apple"]

Event8: "example", 3, ["testing", "this", "example", "apple"]

Event9:  NULL, 4, ["testing", "this", "example"]
Received on Thursday, 29 September 2011 09:21:29 GMT

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