Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Memento Team
Herbert Van...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
W3C Web Architecture: Resour...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
dereference content negotiat...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Resources
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Resources have Representatio...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Resources have Representatio...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Only the Current Representat...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Old Representations are Lost...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Archived Resources Exist
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Archived Resources
http://we...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Finding Archived Resources
G...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Finding Archived Resources
G...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Navigating Archived Resource...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Navigating Archived Resource...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Current and Past Web are Not...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
TBL on Generic vs. Specific ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
In The Beginning… there was ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Limited Time Semantics…
% te...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Time Semantics Becoming Less...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Past Links to the Presen...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Past Links to the Presen...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
But the Present Does Not Lin...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Linking the Past and the Pre...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Normal HTTP Flow
GET R
200 OK
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Normal HTTP Flow
GET R
200 OK
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Web without a Time Dimen...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Web without a Time Dimen...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Web without a Time Dimen...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Web with Time Dimension ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Web with Time Dimension ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
• Many systems support conte...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento HTTP Flow
HEAD R, Accept-Datetime
302M, Vary, LinkR,B,M
200, Memento-Datetime, LinkR,B,M
GET G, Accept-Datetime...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
The Memento Framework
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Why Not Bypass URI-R and Go ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Long Tail of Archives
A: The...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Transition Period
• Up until...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Client, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Server, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Server, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Compliant Server, Non-Compli...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Some Issues
• Observational ...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
No Uncertainty With Self-Arc...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
foo.html @ t4
t0
|
t1
|
t2
|...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
foo.html @ t4
t0
|
t1
|
t2
|...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Uncertainty in Third-Party A...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Missed Updates
t0
|
t1
|
t2
...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
foo.html @ t4
t0
|
t1
|
t2
|...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
foo.html @ t4
t0
|
t1
|
t2
|...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
foo.html @ t4
t0
|
t1
|
t2
|...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Decrease Uncertainty With Mo...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Three Notions of Time: Cr, L...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Cr == MD == LM
Cr
MD
LM
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Cr == MD < LM
Cr
MD
LM
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
MD < Cr <= LM
Cr
MD
LM
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Cr < MD <= LM
Cr
MD
LM
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
When is the Past?
easy
chall...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Why Care About The Past?
Fro...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Replaying the Experience…
…c...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
vs.
(thanks to Michele Weigl...
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento: Time Travel for the Web
UNC Scholarly Communications Working Group, November 10 2010
Memento wants to make naviga...
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Memento: Time Travel for the Web

  1. 1. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Memento Team Herbert Van de Sompel Michael L. Nelson Robert Sanderson Lyudmila Balakireva Scott Ainsworth Harihar Shankar Memento: Time Travel for the Web Memento is partially funded by the Library of Congress
  2. 2. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 W3C Web Architecture: Resource – URI - Representation Resource Representation Represents URI Identifies dereference
  3. 3. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 dereference content negotiation W3C Web Architecture: Resource – URI - Representation Resource URI Identifies Representation 1 Represents Representation 2Represents
  4. 4. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Resources
  5. 5. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Resources have Representations
  6. 6. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Resources have Representations that Change over Time
  7. 7. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Only the Current Representation is Available from a Resource
  8. 8. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Old Representations are Lost Forever
  9. 9. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Archived Resources Exist
  10. 10. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Archived Resources http://web.archive.org/web/20010911203610/http://ww w.cnn.com/ archived resource for http://cnn.com http://en.wikipedia.org/w/index.php?title=September_1 1_attacks&oldid=282333 archived resource for http://en.wikipedia.org/wiki/September_11_attacks Sep 11 2001, 20:36:10 UTC Dec 20 2001, 4:51:00 UTC
  11. 11. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Finding Archived Resources Go to http://www.archive.org/ and search http://cnn.com On http://web.archive.org/web/*/http://cnn.com, select desired datetime
  12. 12. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Finding Archived Resources Go to http://en.wikipedia.org/wiki/September_11_attacks and click History Browse History
  13. 13. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Navigating Archived Resources http://en.wikipedia.org/w/index.php?title=September_1 1_attacks&oldid=282333 archived resource for http://en.wikipedia.org/wiki/September_11_attacks3 Dec 20 2001, 4:51:00 UTC http://en.wikipedia.org/wiki/The_Pentagon current Pentagon
  14. 14. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Navigating Archived Resources http://web.archive.org/web/20010911203610/http://ww w.cnn.com/ archived resource for http://cnn.com http://web.archive.org/web/20010911213855/www.cnn .com/TECH/space/ Sep 11 2001, 20:36:10 UTC Sep 11 2001, 21:38:55 UTC SPACE
  15. 15. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Current and Past Web are Not Integrated • Current and Past Web based on same technology. • But, going from Current to Past Web is a matter of (manual) discovery. • Memento wants to make going from Current to Past Web a (HTTP) protocol matter. • Memento wants to integrate Current And Past Web.
  16. 16. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 TBL on Generic vs. Specific Resources http://www.w3.org/DesignIssues/Generic.html
  17. 17. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 In The Beginning… there was the inode struct stat { dev_t st_dev; /* ID of device containing file */ ino_t st_ino; /* inode number */ mode_t st_mode; /* protection */ nlink_t st_nlink; /* number of hard links */ uid_t st_uid; /* user ID of owner */ gid_t st_gid; /* group ID of owner */ dev_t st_rdev; /* device ID (if special file) */ off_t st_size; /* total size, in bytes */ blksize_t st_blksize; /* blocksize for filesystem I/O */ blkcnt_t st_blocks; /* number of blocks allocated */ time_t st_atime; /* time of last access */ time_t st_mtime; /* time of last modification */ time_t st_ctime; /* time of last status change */ };
  18. 18. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Limited Time Semantics… % telnet www.digitalpreservation.gov 80 Trying 140.147.249.7... Connected to www.digitalpreservation.gov. Escape character is '^]'. HEAD /images/ndiipp_header6.jpg HTTP/1.1 Host: www.digitalpreservation.gov Connection: close HTTP/1.1 200 OK Date: Mon, 19 Jul 2010 21:41:04 GMT Server: Apache Last-Modified: Thu, 18 Jun 2009 16:25:54 GMT ETag: "1bc861-10935-dca24880" Accept-Ranges: bytes Content-Length: 67893 Connection: close Content-Type: image/jpeg Connection closed by foreign host.
  19. 19. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Time Semantics Becoming Less, Not More Available % telnet www.digitalpreservation.gov 80 Trying 140.147.249.7... Connected to www.digitalpreservation.gov. Escape character is '^]'. HEAD / HTTP/1.1 Host: www.digitalpreservation.gov Connection: close HTTP/1.1 200 OK Date: Mon, 19 Jul 2010 21:36:00 GMT Server: Apache Accept-Ranges: bytes Connection: close Content-Type: text/html Connection closed by foreign host.
  20. 20. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Past Links to the Present… explicit HTML link; no HTTP links; opaque URI
  21. 21. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Past Links to the Present… no HTML links; no HTTP links; implicit from URI
  22. 22. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 But the Present Does Not Link to the Past % telnet www.digitalpreservation.gov 80 Trying 140.147.249.7... Connected to www.digitalpreservation.gov. Escape character is '^]'. HEAD / HTTP/1.1 Host: www.digitalpreservation.gov Connection: close HTTP/1.1 200 OK Date: Mon, 19 Jul 2010 21:36:00 GMT Server: Apache Accept-Ranges: bytes Connection: close Content-Type: text/html Connection closed by foreign host. no hints in HTML, HTTP, or URI
  23. 23. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  24. 24. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  25. 25. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Linking the Past and the Present • Codify existing methods to create linkage from the past to the present – easy: an archived version knows for which URI it is an archived version • Create a linkage from the present to the past – hard: solve with a level of indirection from present to past
  26. 26. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Normal HTTP Flow GET R 200 OK
  27. 27. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Normal HTTP Flow GET R 200 OK
  28. 28. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Web without a Time Dimension 28
  29. 29. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Web without a Time Dimension 29
  30. 30. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Web without a Time Dimension 30 Need to use a different URI to access archived versions of a resource and its current version
  31. 31. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Web with Time Dimension added by Memento 31 In Memento: use URI of the current version to access archived versions, but qualify it with datetime
  32. 32. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Web with Time Dimension added by Memento 32 … and arrive at an archived version via level of indirection TimeGate
  33. 33. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 • Many systems support content negotiation for media type: o Your client by default asks for HTML and gets HTML; o But it could get PDF via the same URI. • Memento proposes a new dimension for content negotiation – time: o Your client by default asks for the current time, and gets it o But it could get an older version via the same URI • Can be accomplished with two new HTTP headers: o Request header: Accept-Datetime o Conveys datetime of content requested by client o Response header: Memento-Datetime o Conveys datetime of content returned by server 33 Content Negotiation in the datetime dimension
  34. 34. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  35. 35. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  36. 36. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  37. 37. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  38. 38. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  39. 39. Memento HTTP Flow HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  40. 40. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 The Memento Framework
  41. 41. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Why Not Bypass URI-R and Go Directly to TimeGate? • The Original Resource (URI-R) might know a "better" TimeGate than the default client value – a CMS (e.g., a wiki) or transactional archive will always have the most complete archival coverage for a URI-R – the client can always ignore the URI-R's TimeGate suggestion • Summary: it is good design to check with URI-R before using the default the TimeGate
  42. 42. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Long Tail of Archives A: There is no one true TimeGate. We envision a competitive marketplace for TimeGates and Aggregators. Q: Which TimeGate should my server (or client) Link to?
  43. 43. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Transition Period • Up until now, we've presented the scenario where both the client and server are compliant with the Memento framework • Good news: Memento elegantly handles scenarios where either the client or the server are not (yet) compliant
  44. 44. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200
  45. 45. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200
  46. 46. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200Client detects absence of Link header in response from URI-R, discards it, then constructs its own URI-G value
  47. 47. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200
  48. 48. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200
  49. 49. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Client, Non-Compliant Server HEAD R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200
  50. 50. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Server, Non-Compliant Client GET R 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  51. 51. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Server, Non-Compliant Client GET R 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  52. 52. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Compliant Server, Non-Compliant Client GET R, Accept-Datetime 302M, Vary, LinkR,B,M 200, Memento-Datetime, LinkR,B,M GET G, Accept-Datetime GET M, Accept-Datetime 200, LinkG
  53. 53. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Some Issues • Observational uncertainty • Different notions of time • When is the past?
  54. 54. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 No Uncertainty With Self-Archiving Systems t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html foo.html pic.gif foo.html pic.gif foo.html has <img src=pic.gif> pic.gif
  55. 55. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 foo.html @ t4 t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html foo.html pic.gif foo.html pic.gif foo.html has <img src=pic.gif> pic.gif GET /foo.html Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t4 GET /pic.gif Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t0
  56. 56. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 foo.html @ t4 t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html foo.html pic.gif foo.html pic.gif foo.html has <img src=pic.gif> pic.gif GET /foo.html Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t4 GET /pic.gif Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t0 foo.html correct pic.gif correct
  57. 57. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Uncertainty in Third-Party Archives t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html foo.html pic.gif foo.html pic.gif foo.html has <img src=pic.gif> pic.gif
  58. 58. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Missed Updates t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html pic.gif foo.html pic.gif pic.gif foo.html pic.gif foo.html has <img src=pic.gif> foo.html pic.gif red italics = missed updates
  59. 59. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 foo.html @ t4 t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html pic.gif foo.html pic.gif pic.gif foo.html pic.gif foo.html has <img src=pic.gif> foo.html pic.gif GET /foo.html Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t4 GET /pic.gif Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t0
  60. 60. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 foo.html @ t4 t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html pic.gif foo.html pic.gif pic.gif foo.html pic.gif foo.html has <img src=pic.gif> foo.html pic.gif GET /foo.html Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t4 GET /pic.gif Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t0 foo.html correct pic.gif incorrect (should be t4)
  61. 61. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 foo.html @ t4 t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html pic.gif foo.html pic.gif pic.gif foo.html pic.gif foo.html has <img src=pic.gif> foo.html pic.gif GET /foo.html Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t4 GET /pic.gif Accept-Datetime: t4 HTTP/1.1 200 OK Memento-Datetime: t0 foo.html correct pic.gif incorrect (should be t4) this combination (foo@t4, pic@t0) never existed!
  62. 62. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Decrease Uncertainty With More Observations? t0 | t1 | t2 | t3 | t4 | t5 | t6 | t7 | foo.html pic.gif foo.html pic.gif foo.html pic.gif pic.gif foo.html pic.gif foo.html has <img src=pic.gif> foo.html pic.gif red italics = missed updates
  63. 63. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Three Notions of Time: Cr, LM, MD • Creation (Cr): datetime when the resource first came into being • Last-Modified (LM): when the resource was last changed • Memento-Datetime (MD): the datetime that the resource was (meaningfully) observed on the web – not the same as the datetime that the resource is "about"; i.e. there is no "Memento-Datetime: Thu, 04 Jul 1776 14:37:00"
  64. 64. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Cr == MD == LM Cr MD LM
  65. 65. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Cr == MD < LM Cr MD LM
  66. 66. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 MD < Cr <= LM Cr MD LM
  67. 67. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Cr < MD <= LM Cr MD LM
  68. 68. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 When is the Past? easy challenging challenging doable but hard tough yikes! cf. the "chronoscope" in Asimov's "The Dead Past"
  69. 69. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Why Care About The Past? From an anonymous reviewer (emphasis mine): "Is there any statistics to show that many or a good number of Web users would like to get obsolete data or resources? "
  70. 70. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Replaying the Experience… …can be more compelling than a summary
  71. 71. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  72. 72. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 vs. (thanks to Michele Weigle for the following Memento selection)
  73. 73. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  74. 74. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  75. 75. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  76. 76. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  77. 77. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  78. 78. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  79. 79. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  80. 80. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  81. 81. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  82. 82. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  83. 83. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  84. 84. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010
  85. 85. Memento: Time Travel for the Web UNC Scholarly Communications Working Group, November 10 2010 Memento wants to make navigating the Web’s Past Easy 85 http://www.mementoweb.org http://groups.google.com/group/memento-dev
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