1. Example: Recognizing Five Letters
A, B, C, D, E
Example features:
x: Number of curved segments
y: Number of straight segments
Where would “F” fall?
Suggest an additional feature
Straight strokes E B 4 3 2 1 A D
Curved
strokes C
Oct. 2016
Recommender Systems: Sci/Tech

2. Fingerprint Classification and Matching
Needed for criminal investigations and biometric identification
Does a fingerprint match any of the prints in a criminal database?
Does the fingerprint match one recorded for an authorized user?
Ridge
Human fingerprints tend to be unique
Even identical twins have different prints
Oct. 2016
Recommender Systems: Sci/Tech

3. Searching the Worldwide Web
Google has indexed the entire contents of the Web
a b c b b b a b c b a b b c a a b c b a b c b a b c b b
a a b 14
a b b 10
a b c 0, 6, 15, 19, 23
b a b 5, 9, 18, 22
b b a 4
b b b 3
b b c 11
b c a 12
b c b 1, 7, 16, 20, 24
c a a 13
c b a 8, 17, 21
c b b 2, 25
Find all occurrences of the
pattern “abcbab”
a b c 0, 6, 15, 19, 23
b c b 1, 7, 16, 20, 24
c b a 8, 17, 21
b a b 5, 9, 18, 22
Common words are included in the index
Uncommon words, or meaningless strings, are indexed by using tuples of letters in the indices
a b c 0, 6, 15, 19, 23
b c b 1, 7, 16, 20, 24
c b a , 17, 21
b a b 5, 9, 18, 22
Oct. 2016
Recommender Systems: Sci/Tech

4. Google’s “Pagerank” Algorithm
Algorithm to rank the hits so that the most useful ones come first
Google also takes your profile, interests, and previous searches
into account
Oct. 2016
Recommender Systems: Sci/Tech