ApacheCon 2009 talk describing methods for doing intelligent (well, really clever at least) search on items with no or poor meta-data.

1. Intelligent Search

2. Intelligent Search
(or at least really clever)

3. Some Preliminaries
• Text retrieval = matrix multiplication
A: our corpus
documents are rows
terms are columns

4. Some Preliminaries
• Text retrieval = matrix multiplication
for each document d:
for each term t:
sd += adt qt
A: our corpus
documents are rows
terms are columns

5. Some Preliminaries
• Text retrieval = matrix multiplication
A: our corpus
documents are rows
terms are columns
sd = Σt adt qt

6. Some Preliminaries
• Text retrieval = matrix multiplication
A: our corpus
documents are rows
terms are columns
s = A q

7. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns

8. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns
Users who bought items
in the list h also bought
items in the list r

9. More Preliminaries
• Recommendation = Matrix multiply
for each user u:
for each item t1:
for each item t2:
rt1 += au,t1 au,t2 ht2
A: our users’ histories
users are rows
items are columns

10. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns
sd = Σt2 Σu au,t1 au,t2 qt2

11. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns
s = A’ (A q)

12. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns
s = (A’A) q

13. More Preliminaries
• Recommendation = Matrix multiply
A: our users’ histories
users are rows
items are columns
s = (A’A) q ish!

14. Why so ish?
• In real life, ish happens because:
• Big data ... so we selectively sample
• Sparse data ... so we smooth
• Finite computers ... so we sparsify
• Top-40 effect ... so we use some stats

15. The same in spite of ish
• The shape of the computation is unchanged
• The cost of the computation is unchanged
• Broad algebraic conclusions still hold

16. Back to recommendations ...

17. Dyadic Structure
● Functional
– Interaction: actor -> item*
● Relational
– Interaction ⊆ Actors x Items
● Matrix
– Rows indexed by actor, columns by item
– Value is count of interactions
● Predict missing observations

18. Fundamental Algorithmics
● Cooccurrence
● A is actors x items, K is items x items
● Product has general shape of matrix
● K tells us “users who interacted with x also
interacted with y”

19. Fundamental Algorithmic Structure
● Cooccurrence
● Matrix approximation by factoring
● LLR

20. But Wait ...

21. But Wait ...
Does it have to be that way?

22. What we have:
For a user who watched/bought/listened to this

23. What we have:
For a user who watched/bought/listened to this
Sum over all other users who watched/bought/...

24. What we have:
For a user who watched/bought/listened to this
Sum over all other users who watched/bought/...
Add up what they watched/bought/listened to

25. What we have:
For a user who watched/bought/listened to this
Sum over all other users who watched/bought/...
Add up what they watched/bought/listened to
And recommend that

26. What we have:
For a user who watched/bought/listened to this
Sum over all other users who watched/bought/...
Add up what they watched/bought/listened to
And recommend that
ish

27. What we have:
Add up what they watched/bought/listened to

28. What we have:
Add up what they watched/bought/listened to
But wait, we can do that faster

29. What we have:
Add up what they watched/bought/listened to
But wait, we can do that faster

30. But why not ...

31. But why not ...

32. But why not ...
Why just dyadic learning?

33. But why not ...
Why just dyadic learning?
Why not triadic learning?

34. But why not ...
Why just dyadic learning?
Why not p-adic learning?

35. For example
● Users enter queries (A)
– (actor = user, item=query)
● Users view videos (B)
– (actor = user, item=video)
● AʼA gives query recommendation
– “did you mean to ask for”
● BʼB gives video recommendation
– “you might like these videos”

36. The punch-line
● BʼA recommends videos in response to a query
– (isnʼt that a search engine?)
– (not quite, it doesnʼt look at content or meta-data)

37. Real-life example
● Query: “Paco de Lucia”
● Conventional meta-data search results:
– “hombres del paco” times 400
– not much else
● Recommendation based search:
– Flamenco guitar and dancers
– Spanish and classical guitar
– Van Halen doing a classical/flamenco riff

38. Real-life example

39. Real-life example

40. System Diagram
Viewing Logs
t user video
Search Logs
t user query-term
selective
sampler
selective
sampler
count
count
join on
user
count
Related videos
v => v1 v2...
Related terms
v => t1 t2...
llr +
sparsify
Hadoop

41. Indexing
Related videos
v => v1 v2...
Video meta
v => url title...
join on
video
Lucene Index
Related terms
v => t1 t2...
Hadoop Lucene (+Katta?)

42. Hypothetical Example
● Want a navigational ontology?
● Just put labels on a web page with traffic
– This gives A = users x label clicks
● Remember viewing history
– This gives B = users x items
● Cross recommend
– BʼA = click to item mapping
● After several users click, results are whatever
users think they should be

43. Resources
● My blog
– http://tdunning.blogspot.com/
● The original LLR in NLP paper
– Accurate Methods for the Statistics of Surprise and Coincidence
(check on citeseer)
● Source code
– Mahout project
– contact me (tdunning@apache.org)