Confidence score calculation

Fixes pelias/pelias#120

controller/search.js

@@ -26,13 +26,14 @@ function setup( backend, query ){
     }
 
     // query backend
-    service.search( backend, cmd, function( err, docs ){
+    service.search( backend, cmd, function( err, docs, meta ){
 
       // error handler
       if( err ){ return next( err ); }
 
       req.results = {
-        data: docs
+        data: docs,
+        meta: meta
       };
 
       next();

helper/geojsonify.js

@@ -16,7 +16,8 @@ var DETAILS_PROPS = [
   'county',
   'localadmin',
   'locality',
-  'neighbourhood'
+  'neighbourhood',
+  'confidence'
 ];
 
 var META_MAP = {

middleware/confidenceScore.js

@@ -0,0 +1,255 @@
+/**
+ *
+ *Basic confidence score should be computed and returned for each item in the results.
+ * The score should range between 0-1, and take into consideration as many factors as possible.
+ *
+ * Some factors to consider:
+ *
+ * - number of results from ES
+ * - score of item within the range of highest-lowest scores from ES (within the returned set)
+ * - linguistic match of query
+ * - detection (or specification) of query type. i.e. an address shouldn't match an admin address.
+ */
+
+var stats = require('stats-lite');
+var logger = require('pelias-logger').get('api');
+
+var RELATIVE_SCORES = true;
+
+function setup(peliasConfig) {
+  RELATIVE_SCORES = peliasConfig.relativeScores || true;
+  return computeScores;
+}
+
+function computeScores(req, res, next) {
+  // do nothing if no result data set
+  if (!req.results || !req.results.data || !req.results.meta) {
+    return next();
+  }
+
+  // compute standard deviation and mean from all scores
+  var scores = req.results.meta.scores;
+  var stdev = computeStandardDeviation(scores);
+  var mean = stats.mean(scores);
+
+  // loop through data items and determine confidence scores
+  req.results.data = req.results.data.map(computeConfidenceScore.bind(null, req, mean, stdev));
+
+  next();
+}
+
+/**
+ * Check all types of things to determine how confident we are that this result
+ * is correct. Score is based on overall score distribution in the result set
+ * as well as how closely the result matches the input parameters.
+ *
+ * @param {object} req
+ * @param {number} mean
+ * @param {number} stdev
+ * @param {object} hit
+ * @returns {object}
+ */
+function computeConfidenceScore(req, mean, stdev, hit) {
+  var dealBreakers = checkForDealBreakers(req, hit);
+  if (dealBreakers) {
+    hit.confidence = 0;
+    return hit;
+  }
+
+  var checkCount = 3;
+  hit.confidence = 0;
+
+  if (RELATIVE_SCORES) {
+    checkCount += 2;
+    hit.confidence += checkDistanceFromMean(hit._score, mean, stdev);
+    hit.confidence += computeZScore(hit._score, mean, stdev);
+  }
+  hit.confidence += checkName(req.clean.input, req.clean.parsed_input, hit);
+  hit.confidence += checkQueryType(req.clean.parsed_input, hit);
+  hit.confidence += checkAddress(req.clean.parsed_input, hit);
+
+  // TODO: look at categories and location
+
+  hit.confidence /= checkCount;
+
+  logger.debug('[confidence]:', hit.confidence, hit.name.default);
+
+  return hit;
+}
+
+function checkForDealBreakers(req, hit) {
+  if (!req.clean.parsed_input) {
+    return false;
+  }
+
+  if (req.clean.parsed_input.state && req.clean.parsed_input.state !== hit.admin1_abbr) {
+    logger.debug('[confidence][deal-breaker]: state !== admin1_abbr');
+    return true;
+  }
+
+  if (req.clean.parsed_input.postalcode && req.clean.parsed_input.postalcode !== hit.zip) {
+    logger.debug('[confidence][deal-breaker]: postalcode !== zip');
+    return true;
+  }
+}
+
+/**
+ * Check how statistically significant the score of this result is
+ * given mean and standard deviation
+ *
+ * @param {number} score
+ * @param {number} mean
+ * @param {number} stdev
+ * @returns {number}
+ */
+function checkDistanceFromMean(score, mean, stdev) {
+  return (score - mean) > stdev ? 1 : 0;
+}
+
+/**
+ * Compare input string or name component of parsed_input against
+ * default name in result
+ *
+ * @param {string} input
+ * @param {object|undefined} parsed_input
+ * @param {object} hit
+ * @returns {number}
+ */
+function checkName(input, parsed_input, hit) {
+  // parsed_input name should take precedence if available since it's the cleaner name property
+  if (parsed_input && parsed_input.name && hit.name.default.toLowerCase() === parsed_input.name.toLowerCase()) {
+    return 1;
+  }
+
+  // if no parsed_input check the input value as provided against result's default name
+  if (hit.name.default.toLowerCase() === input.toLowerCase()) {
+    return 1;
+  }
+
+  // if no matches detected, don't judge too harshly since it was a longshot anyway
+  return 0.7;
+}
+
+/**
+ * Input being set indicates the query was for an address
+ * check if house number was specified and found in result
+ *
+ * @param {object|undefined} input
+ * @param {object} hit
+ * @returns {number}
+ */
+function checkQueryType(input, hit) {
+  if (!!input.number && (!hit.address || (hit.address && !hit.address.number))) {
+    return 0;
+  }
+  return 1;
+}
+
+/**
+ * Determine the quality of the property match
+ *
+ * @param {string|number|undefined|null} inputProp
+ * @param {string|number|undefined|null} hitProp
+ * @param {boolean} expectEnriched
+ * @returns {number}
+ */
+function propMatch(inputProp, hitProp, expectEnriched) {
+
+  // both missing, but expect to have enriched value in result => BAD
+  if (!inputProp && !hitProp && expectEnriched) { return 0; }
+
+  // both missing, and no enrichment expected => GOOD
+  if (!inputProp && !hitProp) { return 1; }
+
+  // input has it, result doesn't => BAD
+  if (inputProp && !hitProp) { return 0; }
+
+  // input missing, result has it, and enrichment is expected => GOOD
+  if (!inputProp && hitProp && expectEnriched) { return 1; }
+
+  // input missing, result has it, enrichment not desired => 50/50
+  if (!inputProp && hitProp) { return 0.5; }
+
+  // both present, values match => GREAT
+  if (inputProp && hitProp && inputProp.toString().toLowerCase() === hitProp.toString().toLowerCase()) { return 1; }
+
+  // ¯\_(ツ)_/¯
+  return 0.7;
+}
+
+/**
+ * Check various parts of the parsed input address
+ * against the results
+ *
+ * @param {object} input
+ * @param {string|number} [input.number]
+ * @param {string} [input.street]
+ * @param {string} [input.postalcode]
+ * @param {string} [input.state]
+ * @param {string} [input.country]
+ * @param {object} hit
+ * @param {object} [hit.address]
+ * @param {string|number} [hit.address.number]
+ * @param {string} [hit.address.street]
+ * @param {string|number} [hit.zip]
+ * @param {string} [hit.admin1_abbr]
+ * @param {string} [hit.alpha3]
+ * @returns {number}
+ */
+function checkAddress(input, hit) {
+  var checkCount = 5;
+  var res = 0;
+
+  if (input && input.number && input.street) {
+    res += propMatch(input.number, (hit.address ? hit.address.number : null), false);
+    res += propMatch(input.street, (hit.address ? hit.address.street : null), false);
+    res += propMatch(input.postalcode, (hit.address ? hit.address.zip: null), true);
+    res += propMatch(input.state, hit.admin1_abbr, true);
+    res += propMatch(input.country, hit.alpha3, true);
+
+    res /= checkCount;
+  }
+  else {
+    res = 1;
+  }
+
+  return res;
+}
+
+/**
+ * z-scores have an effective range of -3.00 to +3.00.
+ * An average z-score is ZERO.
+ * A negative z-score indicates that the item/element is below
+ * average and a positive z-score means that the item/element
+ * in above average. When teachers say they are going to "curve"
+ * the test, they do this by computing z-scores for the students' test scores.
+ *
+ * @param {number} score
+ * @param {number} mean
+ * @param {number} stdev
+ * @returns {number}
+ */
+function computeZScore(score, mean, stdev) {
+  if (stdev < 0.01) {
+    return 0;
+  }
+  // because the effective range of z-scores is -3.00 to +3.00
+  // add 10 to ensure a positive value, and then divide by 10+3+3
+  // to further normalize to %-like result
+  return (((score - mean) / (stdev)) + 10) / 16;
+}
+
+/**
+ * Computes standard deviation given an array of values
+ *
+ * @param {Array} scores
+ * @returns {number}
+ */
+function computeStandardDeviation(scores) {
+  var stdev = stats.stdev(scores);
+  // if stdev is low, just consider it 0
+  return (stdev < 0.01) ? 0 : stdev;
+}
+
+
+module.exports = setup;

package.json

@@ -51,6 +51,7 @@
     "pelias-logger": "^0.0.8",
     "pelias-schema": "1.0.0",
     "pelias-suggester-pipeline": "2.0.2",
+    "stats-lite": "^1.0.3",
     "through2": "0.6.5"
   },
   "devDependencies": {

routes/v1.js

@@ -19,6 +19,7 @@ var controllers     = {
 /** ----------------------- controllers ----------------------- **/
 
 var postProc = {
+  confidenceScores: require('../middleware/confidenceScore'),
   renamePlacenames: require('../middleware/renamePlacenames'),
   geocodeJSON: require('../middleware/geocodeJSON'),
   sendJSON: require('../middleware/sendJSON')
@@ -41,6 +42,7 @@ function addRoutes(app, peliasConfig) {
     search: createRouter([
       sanitisers.search.middleware,
       controllers.search(),
+      postProc.confidenceScores(peliasConfig),
       postProc.renamePlacenames(),
       postProc.geocodeJSON(peliasConfig),
       postProc.sendJSON
@@ -48,6 +50,7 @@ function addRoutes(app, peliasConfig) {
     reverse: createRouter([
       sanitisers.reverse.middleware,
       controllers.search(undefined, reverseQuery),
+      // TODO: add confidence scores
       postProc.renamePlacenames(),
       postProc.geocodeJSON(peliasConfig),
       postProc.sendJSON

service/search.js

@@ -23,20 +23,28 @@ function service( backend, cmd, cb ){
 
     // map returned documents
     var docs = [];
+    var meta = {
+      scores: []
+    };
+
     if( data && data.hits && data.hits.total && Array.isArray(data.hits.hits)){
+
       docs = data.hits.hits.map( function( hit ){
 
+        meta.scores.push(hit._score);
+
         // map metadata in to _source so we
         // can serve it up to the consumer
         hit._source._id = hit._id;
         hit._source._type = hit._type;
+        hit._source._score = hit._score;
 
         return hit._source;
       });
     }
 
     // fire callback
-    return cb( null, docs );
+    return cb( null, docs, meta );
   });
 
 }

test/unit/mock/backend.js

@@ -10,6 +10,7 @@ responses['client/search/ok/1'] = function( cmd, cb ){
   return cb( undefined, searchEnvelope([{
     _id: 'myid1',
     _type: 'mytype1',
+    _score: 10,
     _source: {
       value: 1,
       center_point: { lat: 100.1, lon: -50.5 },
@@ -19,6 +20,7 @@ responses['client/search/ok/1'] = function( cmd, cb ){
   }, {
     _id: 'myid2',
     _type: 'mytype2',
+    _score: 20,
     _source: {
       value: 2,
       center_point: { lat: 100.2, lon: -51.5 },
@@ -35,6 +37,7 @@ responses['client/mget/ok/1'] = function( cmd, cb ){
   return cb( undefined, mgetEnvelope([{
     _id: 'myid1',
     _type: 'mytype1',
+    _score: 10,
     found: true,
     _source: {
       value: 1,
@@ -45,6 +48,7 @@ responses['client/mget/ok/1'] = function( cmd, cb ){
   }, {
     _id: 'myid2',
     _type: 'mytype2',
+    _score: 20,
     found: true,
     _source: {
       value: 2,

test/unit/service/search.js

@@ -19,6 +19,7 @@ module.exports.tests.functional_success = function(test, common) {
   var expected = [
     {
       _id: 'myid1', _type: 'mytype1',
+      _score: 10,
       value: 1,
       center_point: { lat: 100.1, lon: -50.5 },
       name: { default: 'test name1' },
@@ -26,6 +27,7 @@ module.exports.tests.functional_success = function(test, common) {
     }, 
     {
       _id: 'myid2', _type: 'mytype2',
+      _score: 20,
       value: 2,
       center_point: { lat: 100.2, lon: -51.5 },
       name: { default: 'test name2' },