public static List <ModelResult <FoundValue> > FindValues(string utterance, List <SortedValue> values, FindValuesOptions options = null)
{
// Sort values in descending order by length so that the longest value is searched over first.
var list = values;
list.Sort((a, b) => b.Value.Length - a.Value.Length);
// Search for each value within the utterance.
var matches = new List <ModelResult <FoundValue> >();
var opt = options ?? new FindValuesOptions();
var tokenizer = opt.Tokenizer ?? Tokenizer.DefaultTokenizer;
var tokens = tokenizer(utterance, opt.Locale);
var maxDistance = opt.MaxTokenDistance ?? 2;
for (var index = 0; index < list.Count; index++)
{
var entry = list[index];
// Find all matches for a value
// - To match "last one" in "the last time I chose the last one" we need
// to re-search the string starting from the end of the previous match.
// - The start & end position returned for the match are token positions.
var startPos = 0;
var vTokens = tokenizer(entry.Value.Trim(), opt.Locale);
while (startPos < tokens.Count)
{
var match = MatchValue(tokens, maxDistance, opt, entry.Index, entry.Value, vTokens, startPos);
if (match != null)
{
startPos = match.End + 1;
matches.Add(match);
}
else
{
break;
}
}
}
// Sort matches by score descending
matches.Sort((a, b) => (int)(b.Resolution.Score - a.Resolution.Score));
// Filter out duplicate matching indexes and overlapping characters.
// - The start & end positions are token positions and need to be translated to
// character positions before returning. We also need to populate the "text"
// field as well.
var results = new List <ModelResult <FoundValue> >();
var foundIndexes = new HashSet <int>();
var usedTokens = new HashSet <int>();
foreach (var match in matches)
{
// Apply filters
bool add = !foundIndexes.Contains(match.Resolution.Index);
for (var i = match.Start; i <= match.End; i++)
{
if (usedTokens.Contains(i))
{
add = false;
break;
}
}
// Add to results
if (add)
{
// Update filter info
foundIndexes.Add(match.Resolution.Index);
for (var i = match.Start; i <= match.End; i++)
{
usedTokens.Add(i);
}
// Translate start & end and populate text field
match.Start = tokens[match.Start].Start;
match.End = tokens[match.End].End;
// Note: JavaScript Substring is (start, end) whereas .NET is (start, len)
match.Text = utterance.Substring(match.Start, (match.End + 1) - match.Start);
results.Add(match);
}
}
// Return the results sorted by position in the utterance
results.Sort((a, b) => a.Start - b.Start);
return(results);
}
private static ModelResult <FoundValue> MatchValue(List <Token> tokens, int maxDistance, FindValuesOptions options, int index, string value, List <Token> vTokens, int startPos)
{
// Match value to utterance and calculate total deviation.
// - The tokens are matched in order so "second last" will match in
// "the second from last one" but not in "the last from the second one".
// - The total deviation is a count of the number of tokens skipped in the
// match so for the example above the number of tokens matched would be
// 2 and the total deviation would be 1.
var matched = 0;
var totalDeviation = 0;
var start = -1;
var end = -1;
foreach (var token in vTokens)
{
// Find the position of the token in the utterance.
var pos = IndexOfToken(tokens, token, startPos);
if (pos >= 0)
{
// Calculate the distance between the current tokens position and the previous tokens distance.
var distance = matched > 0 ? pos - startPos : 0;
if (distance <= maxDistance)
{
// Update count of tokens matched and move start pointer to search for next token after
// the current token.
matched++;
totalDeviation += distance;
startPos = pos + 1;
// Update start & end position that will track the span of the utterance that's matched.
if (start < 0)
{
start = pos;
}
end = pos;
}
}
}
// Calculate score and format result
// - The start & end positions and the results text field will be corrected by the caller.
ModelResult <FoundValue> result = null;
if (matched > 0 && (matched == vTokens.Count || options.AllowPartialMatches))
{
// Percentage of tokens matched. If matching "second last" in
// "the second from last one" the completeness would be 1.0 since
// all tokens were found.
var completeness = matched / vTokens.Count;
// Accuracy of the match. The accuracy is reduced by additional tokens
// occurring in the value that weren't in the utterance. So an utterance
// of "second last" matched against a value of "second from last" would
// result in an accuracy of 0.5.
var accuracy = (matched / (matched + totalDeviation));
// The final score is simply the completeness multiplied by the accuracy.
var score = completeness * accuracy;
// Format result
result = new ModelResult <FoundValue>
{
Start = start,
End = end,
TypeName = "value",
Resolution = new FoundValue
{
Value = value,
Index = index,
Score = score
}
};
}
return(result);
}
