Browsing and Recomposition Policies to Minimize Temporal Error When Utilizing Web Archives

BROWSING AND
RECOMPOSITION POLICIES
TO MINIMIZE TEMPORAL
ERROR WHEN UTILIZING
WEB ARCHIVES
SCOTT G. AINSWORTH
OLD DOMINION UNIVERSITY
COMPUTER SCIENCE
JCDL 2013
JULY 23-25, 2013
INDIANAPOLIS, INDIANA USA

JointConferenceonDigitalLibraries(JCDL)2013
CONTENTS
 Motivation
 Related work
 Preliminary work
 Future work
 Conclusion
7/23/13 Scott G. Ainsworth • Michael L. Nelson
2

A FABLE FROM WAYBACK
3
A long, long time ago…
ODU Computer Science
updated its web site…
What did it look like?
May 2005...

4

5

6

7

WHAT JUST HAPPENED?
WHAT WE EXPECTED
2005-05-14 @ 01:36:08
WHAT WE GOT
2005-03-31 @ 09:16:10
8

TEMPORAL SPREAD
9
2005-05-
14
01:36:08
+9 days
+18 days +18 days
+7 months
+2.1 years

QUESTIONS
• How much temporal drift do users experience?
• How much temporal spread exists in composite
mementos?
• How can drift and spread be minimized?
• What factors contribute, positively or
negatively, to drift and spread?
• Does combining multiple archives produce
better results?
• Would users with differing goals benefit from
different minimization policies and heuristics?
• How can temporal coherence be displayed to
users—simply?
10

CONTENTS
 Motivation
 Related work
 Future work
 Conclusion
11

RELATED WORK
Web Crawling for Search Engines
• Douglis – Change rates
• Cho – Optimal crawling strategies, change rates,
Web evolution
Web Archiving
• Masanés – Web Archiving: Issues and Methods
• Jaffe & Kirkpatrick – Internet Archive architecture
• Moore et al. – Heritrix crawler
12

RELATED WORK
Control Crawl Data Quality, Future collections
• Spaniol et al. – crawling strategy
• Denev et al. – change rates by MIME type and
depth
• Ben Saad et al. – metadata from crawl used to
select best results from archive
Our Focus: Existing Data Quality
• Existing collections
• Datetime selection policies
13

RELATED WORK
Use Patterns
• AlNoamony et al. – Archive Access Patterns
• Humans vs. Robots
• Dip, dive, slide, & skim
Identifying Duplicates
• Simple identity – images, other binary formats
• direct comparison
• Hash comparison
• HTML, CSS (text)
• Shingling, Jaccard distances, etc.
• SimHash ⃪ most promise
14

RELATED WORK – MEMENTO*
• HTTP extension for datetime negotiation
Request
Response
15
GET <timegate>/http://www.cs.odu.edu/ HTTP/1.1
…
Accept-Datetime: Sat, 10 May 2005 11:21:00 GMT
…
HTTP/1.1 200 OK
…
Memento-Datetime: Sat, 14 May 2005 01:36:08 GMT
…
*https://datatracker.ietf.org/doc/draft-vandesompel-memento/

CONTENTS
 Motivation
 Related work
 How much of the Web is archived
 Temporal Drift
 Temporal Spread
 Future work
 Conclusion
16

HOW MUCH IS ARCHIVED?
17
35 – 90% At least one archived copy
17 – 49% 2 – 5 copies
1 – 8% 6 – 10 copies
8 – 63% > 10 copies JCDL’11
Internet Archive
Search Engine
Other

CONTENTS
 Motivation
 Related work
 Preliminary work
 How much of the Web is archived
 Temporal Drift
 Temporal Spread
 Future work
 Conclusion
18

TEMPORAL DRIFT
Comparing two policies
• Sliding – target datetime changes
• Sticky – target datetime held steady
19

SLIDING TARGET
20
2005-05-14
01:36:08

SLIDING TARGET
21
2005-04-22
00:17:52

SLIDING TARGET
22
2005-03-31
09:16:10

STICKY TARGET
What if the target
is held steady?
(Enabled by Memento API)
23

2005-05-14STICKY TARGET
24
MementoFoxExtension
2005-05-14
01:36:08

STICKY TARGET
25
2005-04-22
00:17:52

STICKY TARGET
26
2005-05-
14
01:36:08

MEDIAN DRIFT BY STEP
Median Drift by Step
Step Number
MedianDrift(Months)
1 10 20 30 40 50
01m2m3m
API
UI
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●
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●
●
●
●
●
●●●
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●●
●●
●●●●●
●
●
●
●
●●●●
●
●
● Sliding
● Sticky
MedianDrift(months)
27
Step Number
JCDL’13

CONTENTS
 Motivation
 Related work
 How much of the Web is archived
 Temporal Drift
 Temporal Spread
 Future work
 Conclusion
28

TEMPORAL SPREAD
29

COMPOSITE MEMENTO
PRESENTATION STRUCTURE
30
URI-M0
URI-M1 URI-M2 URI-Mi-1
...
URI-Mi URI-Mi+1 URI-Mn...

TEMPORAL SPREAD
31
2005-05-
14
01:36:08
+9 days
+18 days +18 days
+7 months
+2.1 years

EMBEDDED RESOURCES
Resource Memento-Datetime Delta Resource
Memento-
Datetime
Delta
http://www.cs.odu.edu 2005-05-14 01:36:08 spacer.gif 2005-06-01 16:23:10 18.6 d
mm_menu.js 2005-05-23 02:39:12 9.0 d jimcheng.gif 2005-06-01 16:37:39 18.6 d
style.css 2005-05-23 02:39:39 9.0 d jsmith.gif 2005-06-01 16:58:50 18.6 d
gfx-logo-odu-crown.gif 2005-05-23 02:39:39 9.0 d rmenu_1st_featured_alumni.png 2005-06-01 21:21:45 18.8 d
ddmenu_ddown.js 2005-05-23 02:39:43 9.0 d hmenu_college_...-new.png 2005-12-21 20:14:25 7.3 mo
university.js 2005-05-23 02:39:56 9.0 d rmenu_1st_upcoming_news.png 2005-12-21 20:15:14 7.3 mo
rmenu_1st_about.png 2005-06-01 13:40:25 18.5 d rmenu_1st_upcoming_events.png 2005-12-21 21:01:12 7.3 mo
rmenu_bottom_229.gif 2005-06-01 14:07:29 18.5 d lmenu_1st_resources.png 2005-12-28 17:47:41 7.5 mo
shadow-bl.gif 2005-06-01 14:55:53 18.6 d bullet_blue_triangle.gif 2005-12-28 19:43:48 7.5 mo
ecsbdg.jpg 2005-06-01 14:56:17 18.6 d logo-cs.gif 2005-12-28 19:54:29 7.5 mo
shadow-br.gif 2005-06-01 15:18:18 18.6 d rmenu_1st_featured_student.png 2007-06-12 02:36:07 2.1 years
gfx-btn-go-dblue.gif 2005-06-01 15:34:19 18.6 d shadow-b.gif 2007-06-21 02:35:17 2.1 years
shadow-tr.gif 2005-06-01 15:55:57 18.6 d shadow-r.gif 404 Not Found
header-right1.gif 2005-06-01 16:06:16 18.6 d
32
Embedded Resources 26
Mean Delta 125.9 days
Standard Deviation 207.7 days
Spread 2.1 years

REPRESENTING SPREAD
COMPOSITE MEMENTO
TEMPORAL SPREAD CHART
33
URI-M0
URI-M1 URI-M2 URI-M3
Root
Embedded
Same Domain
Reused

TEMPORAL SPREAD – ODU CS
34

TEMPORAL COHERENCE
35
root emb1
1 Memento, Bracketed Root

TEMPORAL COHERENCE
36
Last-
Modified root emb1

TEMPORAL COHERENCE
37
Last-
Modified
Last-Modified ≤ root ≤ emb1 Þ coherent
root emb1

TEMPORAL COHERENCE
38
1 Memento, Root Not Bracketed
Last-
Modifiedroot emb1

TEMPORAL COHERENCE
39
1 Memento, Root Not Bracketed
Last-
Modified
root ≤ Last-Modified ≤ emb1 Þ violation
root emb1

TEMPORAL COHERENCE
40
1 Memento, No Last-Modified

TEMPORAL COHERENCE
41
n/a
Last-Modified ≤ emb < root Þ possibly coherent
rootembn
1 Memento, Before Root

TEMPORAL COHERENCE
42
2 Mementos, Root Not Bracketed
Last-
Modifiedroot emb1

TEMPORAL COHERENCE
43
2 Mementos, Root Not Bracketed
Last-
Modified
n/a
root embi+1
embi

TEMPORAL COHERENCE
44
2 Mementos, Use Content – Similarity

TEMPORAL COHERENCE
45
2 Mementos, Contents Equal or Equivalent

TEMPORAL COHERENCE
46
2 Mementos, Contents Not Equal or Equivalent

FIRST EXPERIMENT
• 1,000 URIs from DMOZ (Open Directory)
• Download all timemaps
• Download all composite mementos
• Download all embedded resources
• Single and Multiple Archives
• Four Heuristics
47

PRELIMINARY RESULTS 1
Count Description Percent
1,000 Root URI-Rs
910 Root timemaps 91%
87,847 Root URI-Ms in timemaps
96.5 URI-Ms per Root URI-R
85,570 Root memento downloaded 97%
1,488,420 Embedded URI-Rs
17.4 Embedded URI-Rs per Root memento
48

PRELIMINARY RESULTS 2
Description Minimize
Distance,
Single
Archive
Minimize
Distance,
Multi-
Archive
3-Month
Window,
Multi-
Archive
Embedded URI-Rs 1,488,440 1,488,420 1,447,351
Embedded URI-Ms in timemaps 1,169,787 1,186,456 500,541
URI-M/Embedded URI-R 0.79 0.80 0.35
% Complete 73.8% 75.4% 33.8%
Mean spread 200.2 200.1 15.1
Standard Deviation 219.2 219.9 14.3
49

CURRENT EXPERIMENT
• 4,000 URIs from JCDL’11 “How Much…” paper
• 1 URI/month vice all
• Target WSDM 2013
50

CONTENTS
 Motivation
 Related work
 Future work
 Conclusion
51

FUTURE WORK
Browsing Patterns, Clusters & Drift
• AlNoamany et al. – Real-world access patterns
• Domains users avoid – link farms, etc.
• Domain clusters
52

FUTURE WORK
Timemaps, Redirection, Missing Mementos
• Timemaps only tell part of the story
• URI-R redirection (302 from source)
• URI-M redirection (Archive action)
• Mementos in timemaps but not accessible
• Policies must consider user needs
• Leave it missing
• Show “best” substitute
53

FUTURE WORK
Similarity & Duplication
• Delta are currently | root – embedded |
• If bracketing mementos are identical,
should delta be zero?
• HTML is usually modified by the archive
• Can’t check for equality
• Shingling? SimHash?
54
0 +30d–30d

FUTURE WORK
Communicating Status
55
Coherent Partial Incoherent Missing

FUTURE WORK
Policies & Heuristics
• Drift
• Sliding target
• Sticky target
• Spread
• Minimize distance
• Past only
• Past preferred
• Near or within distance
• Single vs. multi-archive
• Refine to meet user expectations
56

CONTENTS
 Motivation
 Related work
 Future work
 Conclusion
57

CONCLUSION
Extensive research on improving acquisition exists
Best use of existing collections needs study
We are looking at
• Characterizing existing holdings
• Policies that minimize impact of drift and spread
• Characterizing memento and walk status
58

TIMELINE
Spread
Policy
Drift
CIKM
May '13
paper
Nov '13
paper
Feb '14
Missing mementos,
duplicates,
similarity, icon
Ph.D.
dissertation
Candidacy
Aug '13
Defense
Nov '14
paper
Spring '14
"Human" patterns,
clusters, spam sites
59

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