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Enhancing relevancy through personalization & semantic search


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Matching keywords is just step one in the effort to maximize the relevancy of your search platform. In this talk, you'll learn how to implement advanced relevancy techniques which enable your search platform to "learn" from your content and users' behavior. Topics will include automatic synonym discovery, latent semantic indexing, payload scoring, document-to-document searching, foreground vs. background corpus analysis for interesting term extraction, collaborative filtering, and mining user behavior to drive geographically and conceptually personalized search results. You'll learn how CareerBuilder has enhanced Solr (also utilizing Hadoop) to dynamically discover relationships between data and behavior, and how you can implement similar techniques to greatly enhance the relevancy of your search platform.

Published in: Technology, Education

Enhancing relevancy through personalization & semantic search

  1. 1. Dublin, IE 2013.11.07 Trey Grainger ENHANCING RELEVANCY THROUGH PERSONALIZATION & SEMANTIC SEARCH Search Technology Development Manager @  
  2. 2. My Background Trey  Grainger   Search  Technology  Development  Manager     Relevant  Background   •  Search  &  Recommenda>ons   •  High-­‐volume,  Distributed  Systems   •  NLP,  Relevancy  Tuning,  User  Group  Tes>ng,  &  Machine  Learning                                                          Other  Projects   •  Co-­‐author:    Solr  in  Ac*on   •  Founder  and  Chief  Engineer  @                                                    .com  
  3. 3. Roadmap •  •  •  I. How we use Solr @ CareerBuilder II. Traditional Relevancy Scoring III. Advanced Relevancy through functions –  Factors as a linear function –  Context-aware relevancy parameter weighting •  III. Personalization & Recommendations –  Profile and Behavior-based –  Solr as a recommendation engine –  Collaborative Filtering •  IV. Semantic Search –  –  –  –  –  Mining user-behavior for synonyms Uncovering meaning through clustering Latent Semantic Indexing overview Document-based searching Foreground vs. Background analysis
  4. 4. How  we  use  Solr  @  CareerBuilder  
  5. 5. Search Scale @ •  •  •  •  •  •  Over  2.5  million  new  jobs  each  month     Over  60  million  ac>vely  searchable  resumes   ~300  globally  distributed  search  servers     Thousands  of  unique,  dynamically  generated  indexes   Over  1  Billion  ac>vely  searchable  documents   Over  1  million  searches  an  hour  
  6. 6. Data Analytics
  7. 7. Data Analytics
  8. 8. Data Analytics (market supply)
  9. 9. Data Analytics (market demand)
  10. 10. Data Analytics (labor pressure: supply/demand)
  11. 11. Data Analytics (hiring comparison per market)
  12. 12. Traditional Search
  13. 13. Recommendations
  14. 14. Tradi>onal  Relevancy  Scoring  
  15. 15. Default Lucene Relevancy Algorithm (DefaultSimilarity) Score(q,d)  =                  ∑    (  -(t  in  d)  ·∙    idf(t)2  ·∙  t.getBoost()  ·∙  norm(t,  d)  )  ·∙  coord(q,  d)  ·∙  queryNorm(q)          t  in  q             Where:      t  =  term;  d  =  document;  q  =  query;  f  =  field                    -(t  in  d)    =    numTermOccurrencesInDocument  ½                    idf(t)  =    1  +  log  (numDocs  /  (docFreq  +  1))                    coord(q,  d)  =  numTermsInDocumentFromQuery  /  numTermsInQuery                    queryNorm(q)  =  1  /  (sumOfSquaredWeights  ½  )                    sumOfSquaredWeights  =  q.getBoost()2  ·∙  ∑  (  idf(t)  ·∙  t.getBoost()  )2                                                                                                                                                                                                                                                                                                                                                                                  t  in  q                    norm(t,  d)      =      d.getBoost()    ·∙    lengthNorm(f)    ·∙      f.getBoost()   *Source:  Solr  in  Ac*on,  chapter  3    
  16. 16. TF * IDF •  Term Frequency: “How well a term describes a document?” –  Measure: how often a term occurs per document •  Inverse Document Frequency: “How important is a term overall?” –  Measure: how rare the term is across all documents
  17. 17. Boosting documents and fields •  Certain fields may be more important than other fields: –  The Job Title and Skills may be more relevant than other aspects of the job: /select?qf=jobtitle^10 skills^5 jobrequirements^2 jobdescription^1 •  It’s possible to boost documents and fields at both index time and query time •  If you need more fine-grained control (such as per-term index-time boosting), you can make use of payloads
  18. 18. Custom scoring with Payloads •  In addition to boosting search terms and fields, content within Fields can also be boosted differently using Payloads (requires a custom scoring implementation): design [1] / engineer [1] / really [ ] / great [ ] / job [ ] / ten[3] / years[3] / experience[3] / careerbuilder [2] / design [2], … jobtitle: bucket=[1] boost=10; company: bucket=[2] boost=4; jobdescription: bucket=[ ] weight=1; experience: bucket=[3] weight=1.5 We can pass in a parameter to solr at query time specifying the boost to apply to each bucket i.e. …&bucketWeights=1:10;2:4;3:1.5;default:1; •  This allows us to map many relevancy buckets to search terms at index time and adjust the weighting at query time without having to search across hundreds of fields. •  By making all scoring parameters overridable at query time, we are able to do A / B testing to consistently improve our relevancy model
  19. 19. That’s great, but what about domain-specific knowledge? •  •  •  •  •  News search: popularity and freshness drive relevance Restaurant search: geographical proximity and price range are critical Ecommerce: likelihood of a purchase is key Movie search: More popular titles are generally more relevant Job search: category of job, salary range, and geographical proximity matter TF * IDF of keywords can’t hold it’s own against good domain-specific relevance factors!
  20. 20. Advanced  Relevancy  through  Func>ons  
  21. 21. Example of domain-specific relevancy calculation News website: /select? fq=$myQuery& 25%   q=_query_:"{!func}scale(query($myQuery),0,100)" AND _query_:"{!func}div(100,map(geodist(),0,1,1))" 25%   AND _query_:"{!func}recip(rord(publicationDate),0,100,100)" 25%   AND _query_:"{!func}scale(popularity,0,100)"& myQuery="street festival"& 25%   sfield=location& pt=33.748,-84.391 *Example  from  chapter  16  of  Solr  in  Ac*on  
  22. 22. Fancy boosting functions •  Separating “relevancy” and “filtering” from the query: q=_val_:"$keywords"&fq={!cache=false v=$keywords}&keywords=solr •  Keywords (50%) + distance (25%) + category (25%) q=_val_:"scale(mul(query($keywords),1),0,50)" AND _val_:"scale(sum($radiusInKm,mul(query($distance),-1)),0,25)” AND _val_:"scale(mul(query($category),1),0,25)" &keywords=solr &radiusInKm=48.28 &distance=_val_:"geodist(latitudelongitude.latlon_is,33.77402,-84.29659)” &category=jobtitle:"java developer" &fq={!cache=false v=$keywords}
  23. 23. Context aware relevancy Example: Willingness to relocate for a job 2,500   2,000   1,500   1,000   500   0   So>ware  engineers   Food  service  workers   1%   5%   10%   20%   25%   30%   40%   50%   60%   70%   75%   80%   90%   95%  
  24. 24. Willingness to relocate Somware  engineers  in  Chicago  want  jobs  in  these  loca>ons:  
  25. 25. Willingness to relocate Food  service  workers  in  Chicago  want  jobs  in  these  loca>ons:  
  26. 26. Personaliza>on  &  Recommenda>ons  
  27. 27. Beyond domain knowledge… consider per-user knowledge •  John lives in Boston but wants to move to New York or possibly another big city. He is currently a sales manager but wants to move towards business development. •  Irene is a bartender in Dublin and is only interested in jobs within 10KM of her location in the food service industry. •  Irfan is a software engineer in Atlanta and is interested in software engineering jobs at a Big Data company. He is happy to move across the U.S. for the right job. •  Jane is a nurse educator in Boston seeking between $40K and $60K working in the healthcare industry
  28. 28. Query for Jane Jane is a nurse educator in Boston seeking between $40K and $60K working in the healthcare industry http://localhost:8983/solr/jobs/select/? fl=jobtitle,city,state,salary& q=( jobtitle:"nurse educator"^25 OR jobtitle:(nurse educator)^10 ) AND ( (city:"Boston" AND state:"MA")^15 OR state:"MA”) AND _val_:"map(salary, 40000, 60000,10, 0)” *Example from chapter 16 of Solr in Action
  29. 29. Search Results for Jane { ... "response":{"numFound":22,"start":0,"docs":[ {"jobtitle":"Clinical Educator (New England/ Boston)", "city":"Boston", "state":"MA", "salary":41503}, {"jobtitle":"Nurse Educator", "city":"Braintree", "state":"MA", "salary":56183}, {"jobtitle":"Nurse Educator", "city":"Brighton", "state":"MA", "salary":71359} …]}} *Example documents available @  
  30. 30. What did we just do? •  We built a recommendation engine! •  What is a recommendation engine? –  A system that uses known information (or derived information from that known information) to automatically suggest relevant content •  Our example was just an attribute based recommendation… we’ll see that behavioral-based (i.e. collaborative filtering) is also possible.
  31. 31. Redefining “Search Engine” •  “Lucene is a high-performance, full-featured text search engine library…” Yes,  but  really…   •   Lucene  is  a  high-­‐performance,  fully-­‐featured   token  matching  and  scoring  library…  which   can  perform  full-­‐text  searching.  
  32. 32. Redefining “Search Engine” or,  in  machine  learning  speak:   •  A  Lucene  index  is  mul>-­‐dimensional     sparse  matrix…  with  very  fast  and  powerful  lookup   capabili>es.   •  Think  of  each  field  as  a  matrix  containing  each  term   mapped  to  each  document  
  33. 33. The Lucene Inverted Index (traditional text example) What  you  SEND  to  Lucene/Solr:   How  the  content  is  INDEXED  into   Lucene/Solr  (conceptually):   Document   Content  Field   Term   Documents   doc1     once  upon  a  >me,  in  a  land  far,  far   away   a   doc1  [2x]   brown   doc2   the  cow  jumped  over  the  moon.   doc3  [1x]  ,  doc5  [1x]   cat   doc4  [1x]   doc3     the  quick  brown  fox  jumped  over   the  lazy  dog.   cow   doc2  [1x]  ,  doc5  [1x]   …   ...   doc4   the  cat  in  the  hat   once   doc1  [1x],  doc5  [1x]   doc5   The  brown  cow  said  “moo”  once.   over   doc2  [1x],  doc3  [1x]   the   …   …   doc2  [2x],  doc3  [2x],   doc4[2x],  doc5  [1x]   …   …  
  34. 34. Matching text queries to text fields /solr/select/?q=jobcontent:“software engineer” Job  Content  Field   Documents   …   …   engineer   doc1,  doc3,  doc4,  doc5   engineer   doc5   somware  engineer   …   mechanical   doc2,  doc4,  doc6   …   …   somware   doc1,  doc3,  doc4,  doc7,   doc8   …   …   doc1          doc3                      doc4   somware   doc7          doc8  
  35. 35. Beyond Text Searching •  Lucene/Solr  is  a  search  matching  engine   •  When  Lucene/Solr  search  text,  they  are  matching   tokens  in  the  query  with  tokens  in  index   •  Anything  that  can  be  searched  upon  can  form  the   basis  of  matching  and  scoring:   –  text,  atributes,  loca>ons,  results  of  func>ons,  user   behavior,  classifica>ons,  etc.    
  36. 36. Approaches to Recommendations •  Content-based –  Attribute based i.e. income level, hobbies, location, experience –  Hierarchical i.e. “medical//nursing//oncology”, “animal//dog//terrier” –  Textual Similarity i.e. Solr’s MoreLikeThis Request Handler & Search Handler –  Concept Based i.e. Solr => “software engineer”, “java”, “search”, “open source” •  Collaborative Filtering “Users who liked that also liked this…” •  Hybrid Approaches
  37. 37. Collaborative Filtering What  you  SEND  to  Lucene/Solr:   Document   “Users  who  bought  this  product”  field   doc1     How  the  content  is  INDEXED  into   Lucene/Solr  (conceptually):   Term   Documents   user1,  user4,  user5   user1   doc1,  doc5   doc2   user2,  user3   user2   doc2   doc3     user4   user3   doc2   doc4   user4,  user5   user4   doc5   user4,  user1   doc1,  doc3,     doc4,  doc5   …   …   user5   doc1,  doc4   …   …  
  38. 38. Step 1: Find similar users who like the same documents q=documen>d:  ("doc1"  OR  "doc4")   Document   “Users  who  bought  this  product”  field   doc1     user1,  user4,  user5   doc2   user2,  user3   doc3     user4   doc4   user4,  user5   doc5   user4,  user1   …   …   *Source:  Solr  in  Ac*on,  chapter  16   doc1   user1          user4                              user5   doc4        user4          user5   Top-­‐scoring  results  (most  similar  users):   1)   user4  (2  shared  likes)   2)   user5  (2  shared  likes)   3)   user  1  (1  shared  like)  
  39. 39.   Step 2: Search for docs “liked” by those similar users       Most  similar  users:   1)               ser4      2    s  hared    l  ikes)                    /solr/select/?q=userlikes:("user4"^2              u                (                                               2)   user5  (2  shared  likes)        (1                     ike)   3)   user  1          shared    l                                                                                  OR  "user5"^2  OR  "user1"^1)   Term   Documents   user1   doc1,  doc5   user2   doc2   user3   doc2   user4   doc1,  doc3,     doc4,  doc5   user5   doc1,  doc4   …   …   *Source:  Solr  in  Ac*on,  chapter  16   Top  recommended  documents:   1)  doc1  (matches  user4,  user5,  user1)   2)  doc4  (matches  user4,  user5)   3)  doc5  (matches  user4,  user1)   4)  doc3  (matches  user4)     //  doc2  does  not  match  
  40. 40. Building up to personalization •  Use what you have: –  User’s keywords, IP address, searches, clicks, “likes” (purchases, job applications, comments, etc.) –  Build up a dossier of information on your users –  If a user gives you a profile (resume, social profile, etc), even better.
  41. 41. For full coverage of building a recommendation engine in Solr… •  See my talk from Lucene Revolution 2012 (Boston):
  42. 42. Personalized Search •  Why limit yourself to JUST explicit search or JUST automated recommendations? •  By augmenting your user’s explicit queries with information you know about them, you can personalize their search results. •  Examples: –  A known software engineer runs a blank job search in New York… •  Why not show software engineering higher in the results? –  A new user runs a keyword-only search for nurse •  Why not use the user’s IP address to boost documents geographically closer?
  43. 43. Seman>c  Search  
  44. 44. Not going to talk about… •  Using the SynonymFilter •  Automatic language detection •  Stemming/lemmatization/multi-lingual search •  Stopwords (For all of the above, see the Solr Wiki, Reference Guide, or read Solr in Action) •  Instead, we’re going to cover: –  Mining user behavior to discover synonyms/related queries –  Discovering related concepts using document clustering in Solr –  Future work: Latent Semantic Indexing –  Document to Document searching using More Like This –  Foreground/Background corpus analysis
  45. 45. Automatic Synonym Discovery •  •  Our primary approach: Search Co-occurrences Strategy: Map/Reduce job which computes similar searches run for the same users John searched for “java developer” and “j2ee” Jane searched for “registered nurse” and “r.n.” and “prn”. Zeke searched for “java developer” and “scala” and “jvm” •  By mining the searches of tens millions of search terms per day, we get a list of top searches, with the corresponding top co-occurring searches. •  We also tie each search term to the top category of jobs (i.e java developer, truck driver, etc.), so that we know in what context people search for each term.
  46. 46. Example of “related search terms” Example:  “RN”:   registered  nurse  6588,   rn  registered  nurse  4300,   nurse  2492,   nursing  912,   lpn  707,   healthcare  453,   rn  case  manager  446,   registered  nurse  rn  404,   director  of  nursing  321,   case  manager  292   Example:  “accoun>ng”   accountant  8880,   accounts  payable  5235,   finance  3675,   accoun>ng  clerk  3651,   bookkeeper  3225,   controller  2898,   staff  accountant  2866,   accounts  receivable  2842  
  47. 47. Future work on building conceptual links Latent Semantic Indexing •  Concept: Build a matrix of all terms, perform singular value decomposition on that Matrix to reduce the number of dimensions, and index the meaningful (i.e. blurred) terms on each document. •  Why this matters: if done correctly, the search engine can automatically collapse terms by meaning, remove the useless and redundant ones, and for it’s own conceptual model of your domain space. This can be used to infuse more meaning into a document than just a keyword. •  See blog posts and presentations by John Berryman and Doug Turnbull about their work on this. They’re leading the way on this right now (in the open-source community). •
  48. 48. Using Clustering to find semantic links
  49. 49. Setting up Clustering in solrconfig.xml <searchComponent  name="clustering"  enable=“true“    class="solr.clustering.ClusteringComponent">      <lst  name="engine">          <str  name="name">default</str>          <str  name="carrot.algorithm">    org.carrot2.clustering.lingo.LingoClusteringAlgorithm</str>          <str  name="MultilingualClustering.defaultLanguage">ENGLISH</str>      </lst>   </searchComponent>       <requestHandler  name="/clustering"  enable=“true"  class="solr.SearchHandler">      <lst  name="defaults">          <str  name="clustering.engine">default</str>          <bool  name="clustering.results">true</bool>          <str  name="fl">*,score</str>      </lst>      <arr  name="last-­‐components">          <str>clustering</str>      </arr>   </requestHandler>  
  50. 50. Clustering Query /solr/clustering/?q=(solr or lucene) &rows=100 &carrot.title=titlefield &carrot.snippet=titlefield &LingoClusteringAlgorithm.desiredClusterCountBase=25 //clustering & grouping don’t currently play nicely Allows you to dynamically identify “concepts” and their prevalence within a user’s top search results
  51. 51. Clustering Results Stage  1:  Iden>fy  Concepts   Original  Query:      q=(solr  or  lucene)                      //  can  be  a  user’s  search,  their  job  >tle,    a  list  of  skills,   //  or  any  other  keyword  rich  data  source   Clusters Identified:   Developer (22) Java Developer (13) Software (10) Senior Java Developer (9) Architect (6) Software Engineer (6) Web Developer (5) Search (3)                                             Software Developer (3) Systems (3) Administrator (2) Hadoop Engineer (2) Java J2EE (2) Search Development (2) Software Architect (2) Solutions Architect (2)
  52. 52. Stage  2:  Use  Seman>c  Links  in  your  relevancy  calcula>on   q=content:(“Developer”^22  or  “Java  Developer”^13  or  “Somware   ”^10  or  “Senior  Java  Developer”^9    or  “Architect  ”^6  or  “Somware   Engineer”^6  or  “Web  Developer  ”^5  or  “Search”^3  or  “Somware   Developer”^3  or  “Systems”^3  or  “Administrator”^2  or  “Hadoop   Engineer”^2  or  “Java  J2EE”^2  or  “Search  Development”^2  or   “Somware  Architect”^2  or  “Solu>ons  Architect”^2)     //  Your  can  also  add  the  user’s  loca[on  or  the  original  keywords  to  the     //  recommenda[ons  search  if  it  helps  results  quality  for  your  use-­‐case.  
  53. 53. Document to Document Searching Goal: use an entire document as your Solr Query, recommending other related documents. Standard approach: More Like This Handler Alternative Approach: Foreground vs. Background corpus analysis
  54. 54. More Like This (Query) solrconfig.xml: <requestHandler name="/mlt" class="solr.MoreLikeThisHandler" /> Query: /solr/jobs/mlt/?df=jobdescription& fl=id,jobtitle& rows=3& q=J2EE& // recommendations based on top scoring doc mlt.fl=jobtitle,jobdescription& // inspect these fields for interesting terms mlt.interestingTerms=details& // return the interesting terms mlt.boost=true *Example  from  chapter  16  of  Solr  in  Ac*on  
  55. 55. More Like This (Results) {"match":{"numFound":122,"start":0,"docs":[ {"id":"fc57931d42a7ccce3552c04f3db40af8dabc99dc", "jobtitle":"Senior Java / J2EE Developer"}] }, "response":{"numFound":2225,"start":0,"docs":[ {"id":"0e953179408d710679e5ddbd15ab0dfae52ffa6c", "jobtitle":"Sr Core Java Developer"}, {"id":"5ce796c758ee30ed1b3da1fc52b0595c023de2db", "jobtitle":"Applications Developer"}, {"id":"1e46dd6be1750fc50c18578b7791ad2378b90bdd", "jobtitle":"Java Architect/ Lead Java Developer WJAV Java - Java in Pittsburgh PA"},]},  "interes>ngTerms":[                                "jobdescrip>on:j2ee",1.0,            "jobdescrip>on:java",0.68131137,            "jobdescrip>on:senior",0.52161527,            "job>tle:developer",0.44706684,            "jobdescrip>on:source",0.2417754,            "jobdescrip>on:code",0.17976432,            "jobdescrip>on:is",0.17765637,            "jobdescrip>on:client",0.17331646,            "jobdescrip>on:our",0.11985878,            "jobdescrip>on:for",0.07928475,            "jobdescrip>on:a",0.07875194,            "jobdescrip>on:to",0.07741922,            "jobdescrip>on:and",0.07479082]}}  
  56. 56. More Like This (passing in external document) /solr/jobs/mlt/? df=jobdescription& fl=id,jobtitle& mlt.fl=jobtitle,jobdescription& mlt.interestingTerms=details& mlt.boost=true stream.body=Solr is an open source enterprise search platform from the Apache Lucene project. Its major features include full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document (e.g., Word, PDF) handling. Providing distributed search and index replication, Solr is highly scalable. Solr is the most popular enterprise search engine. Solr 4 adds NoSQL features.
  57. 57. More Like This (Results) {"response":{"numFound":2221,"start":0,"docs":[ {"id":"eff5ac098d056a7ea6b1306986c3ae511f2d0d89 ", •  "jobtitle":"Enterprise Search Architect…"}, {"id":"37abb52b6fe63d601e5457641d2cf5ae83fdc799 ", "jobtitle":"Sr. Java Developer"}, {"id":"349091293478dfd3319472e920cf65657276bda4 ", "jobtitle":"Java Lucene Software Engineer"},]},  "interes>ngTerms":[            "jobdescrip>on:search",1.0,            "jobdescrip>on:solr",0.9155779,            "jobdescrip>on:features",0.36472517,            "jobdescrip>on:enterprise",0.30173126,            "jobdescrip>on:is",0.17626463,            "jobdescrip>on:the",0.102924034,            "jobdescrip>on:and",0.098939896]}  }  
  58. 58. CareerBuilder’s Alternative approach (“enhanced” More Like This) I. Send document as content stream to Solr II. Perform Language Identification on the content III. Do language-specific parts of speech detection •  Keep nouns, remove other parts of speech (removes noise) IV. Do analysis of additional terms for statistical significance: tf * idf OR foreground vs. background corpus comparison OR Both Preferred statistical significance measure: countFG(x) - totalCountFG * probBG(x) z= -------------------------------------------------------sqrt(totalCountFG * probBG(x) * (1 - probBG(x))) V. Return top scoring terms
  59. 59. Foreground vs. Background Corpus Comparison /solr/doc2doc? fg=category:"software engineer"&bg=*:*&stream.body=java nurse and is are was were ruby php solr oncology part-time … other text in a really long document” Terms statistically more likely to appear in foreground query than background query: java ruby We  are  essen>ally  boos>ng  terms  which  are  more  related  to   some  known  feature  (and  ignoring  terms  which  are  equally   php likely  to  appear  in  the  background  corpus)   document Note: This method requires you pre-classify your documents (which we do)… it doesn’t work with a document that hasn’t already been classified.
  60. 60. Pulling it all together Tradi>onal   Search   Personalized   Search   Profit!   Seman>c   Search   Recommenda>ons  
  61. 61. Take-aways •  Lucene’s inverted index is a sparse matrix useful for traditional search (keywords, locations, etc.), recommendations, and discovering links between terms/tokens •  Traditional tf * idf keyword search is a good starting point, but the best relevancy lies in combining your domain knowledge (knowledge of user’s in aggregate) and user-specific knowledge into your own relevancy factors. •  The ability to understand user queries (semantic search) further enhances the search experience, and you already have many tools at your fingertips for this.
  62. 62. Questions? §  Trey  Grainger   @treygrainger           Other  presenta[ons:                h_p://   htp://solrinac>