PageRank Algorithm and

1
PageRank Algorithm and HITS Alogrithm
2
Web?????????

• Web?????????
• ??DB??????????????????????????
• tfidf????????????????????????????
• Web??????????????????????????????
• ????(???????????)?Web(??????)??????
• ???????????????????????????????PageRank?????????

3
PageRank algorithm ?????

• ???????????????????????? ????????????
• ?????????????????????????????(????????????????????
  ???)
• ?
• ??????????????
• ???????????????????????????
• ???????????????????????????????????

4
?????????
10
10515
30
10
5
10
10
10
5
5
???????

• ?????Pi????Pi???????????????????????????
• ????????Pi??????????Pi???????????????????????????
• ?
• ???????????????????????????? R ???????????????????
  ????

6
?????????

• ????A(aij)???
• if ???i?????j???? then aij1/Ni
• (Ni?i????????)
• otherwise aij0
• ???????? R ??????????
• RcAR ???

7
??????1

• 2?????????????????????????????????????????????????
  ??
• ????????????????????????????????
• ?????????????????????????????????
• ?????(15)?????????????????
• ?A??????????????????
• R(cA(1-c)E)R
• E?????1????c0.85?????

8
??????2

• ?????????????????????????
• ?????????????????????????? ? ????
• ?????????????
• PageRank?????????????Web??????????????????????????
  ???????????????????????????????

9
??????????

• R(cA(1-c)E)R
• E?????1????c0.85?????
• ?????????????? R????????????????????????
• R(0)???????
• R(i1)? (cA(1-c)E) R(i)
• D?R(i)?R(i1)
• R(i1)?R(i1)dE
• d? R(i1)?R(i)
• if dgte then goto 2
• ?? x?????????2????v

10
???

• ??????????????(e0.001)
• R? ????????????

1/2?0.18
a 0.365
b0.204
1/2?0.18
1/2?0.102
1?0.321
1/2? 0.102
c0.321
d0.110
11
??

1. a,b,c,d ????????????????????
2. ????????????????0.15??????????????????
3. ?????c??????????a???????
4. ????????????????c???????
5. ???????????????b????????????d???????
6. ?????????????????????????

12
???????

• ???????????????????????????????????????
• Google?10??????100????????????????????????????????
  ??
• ???????????????????????????????????
• Google????????????????
• PC???????????
• ?????????????????????????????????

13
?????(????????????) Lawrence Page, Sergey Brin,
Rajeev Motwani, Terry Winograd, 'The PageRank
Citation Ranking Bringing Order to the Web', 1998

• 1??????
• 107
• 106
• 105
• 0 15
  30 45 ??????

????
161,000,000
322,000,0000
14
HITS algorithm?????

• ??????Web?????????????????????
• TOYOTA?HONDA??????????????????????????
• ???yahoo??????????????????????
• ?????????Web?????????(PageRank?????)
• HITS??????????authorities????authorities???????
  hub ?????????

15
Focused Subgraph -1

• ?????????????S???
• S????????
• ??????
• ?????????????
• ???????(???????)authority page ???
• ????Q???????????????????????????????????????????

16
Focused Subgraph -2

• ???????????20????????
• java???????????????????????????15links
• censorship???????????????????????????28links
• ??link?20019939800????????
• ????

17
Focused Subgraph -3

• ??????????R???????
• R???Q???????? t ???
• SR
• R????????????????(out going link)???? S ???
• R????????????????(in coming link)?????? d
  ???????????? S ???
• Kleinberg????? t200, d50?S?1000 5000???

18
Focused Subgraph -4
S
R
19
Hub ? Authority ???

• S????????Q???????????????????????????
• ????????????????????????????????????????
• ?? authorioty ? hub ????????
• Good hub pages points to many good authority
  pages, good authority pages are pointed to by
  many hubs.
• ??domain???????????????(????????????)

20
weights

• Authority weight of page
• Hub weight of page
• Link set
• Normalization

21
iteration

2. ???????k?????(k20??????)
7. ???

22
???
b
a
c
d

• Authority a3.4610-6, b0.408
• c0.816 , d0.408
• Hub a0.707, b0.707,
• c5.98 10-6, d0

23
?????-1

• ??????????????????????
• ????
• ???????

24
?????-2

• ?????
• ???

25
??Jon M. Klienberg?Authorities Sources in a
Hyperlinked Environment, JACM 46-5 ???

• (java) Authorities
• 0.328 http//www.gamelan.com
• 0.251 http//java.sun.com/
• 0.190 http//www.digitalfocus.com/digitalfocus/
  faq/howdoi.html
• 0.190 http//lightyear.ncsa.unic.edu/srp
  /java/javabooks.html