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revision 1.26 by hemppah, Mon Oct 27 19:15:37 2003 UTC revision 1.27 by benja, Mon Oct 27 19:37:52 2003 UTC
# Line 2  Line 2 
2  Versioning for a location-independent Web: Stopping the shoulders of giants from rotting away  Versioning for a location-independent Web: Stopping the shoulders of giants from rotting away
3  =============================================================================================  =============================================================================================
4    
5  (tentative title)  .. (tentative title)
6    
7    
8    
9  .. contents::  .. contents::
10    
# Line 35  Cassini opponents and supporters [#]_. Line 37  Cassini opponents and supporters [#]_.
37  .. [#] ``http://www.seds.org/spaceviews/cassini/rtgpages.html``.  .. [#] ``http://www.seds.org/spaceviews/cassini/rtgpages.html``.
38     All links dereferenced on October 27th, 2003.     All links dereferenced on October 27th, 2003.
39    
40  Of the 83 links provided by SpaceViews, 29 continue to work in 2003.  Of the 83 links provided by SpaceViews, only 29 continue to work in 2003.
41  Only six years after the launch, two thirds of the debate  Only six years after the launch, almost two thirds of the debate
42  have fallen off the Web. "If I have seen further it is by standing  have fallen off the Web. "If I have seen further it is by standing
43  on the shoulders of giants;" but how can we do that today,  on the shoulders of giants;" but how can we do that today,
44  if the shoulders keep rotting away?  if the shoulders keep rotting away?
# Line 63  to work. Line 65  to work.
65    
66     History of location-dependence: `TBL ref`_ (like in HT'03 paper)     History of location-dependence: `TBL ref`_ (like in HT'03 paper)
67    
68  To accomplish this, links must be made using  This can be accomplished by replacing URIs that include
69  location-independent identifiers: The URI used to make  a server name by location-independent, self-verifying identifiers
70  the link must not specify the server that the page  like cryptographic hashes.
71  is to be downloaded from. The URI of a page must never change,  A file identified by a cryptographic hash
72  even if it moves to a different server.  can be downloaded from any server that has a copy; the client
73    can then check it is the correct file by checking the hash.
74  Instead, identifiers must be *self-verifying*: after downloading  
75  an alleged version of a page from some server, it must be  .. <<<Self-verifying means that given the identifier and a file,
76  possible to *check* that it is really a version of that page.     a client can check that the file matches the identifier.>>>
77  The simplest way to do this is to use a cryptographic hash  
78  to identify the content. After downloading the page, the client  .. <<<(If the hashes do not match, the client can try a different server.)
79  will check it against the cryptographic hash embedded in     This way, a page's URI never needs to change.>>>
 the page's identifier.  
80    
81  In 1996, Tim Berners-Lee [name-myth]_ argued that  In 1996, Tim Berners-Lee [name-myth]_ argued that
82  using location-independent identifiers  using location-independent identifiers
83  is not viable on a global scale:  is not viable on a global scale:
84  "[I]f you put information in a name, it decreases its longevity;  "[I]f you put information in a name, it decreases its longevity;
85  if you don't you can't dereference it to a resource."  if you don't you can't dereference it to a resource."
   
86  However, as we have observed in [fallenstein03storm]_,  However, as we have observed in [fallenstein03storm]_,
87  this assumption has become obsolete with the advent of  with the advent of
88  efficient peer-to-peer lookup mechanisms such as  efficient peer-to-peer lookup mechanisms such as
89  distributed hashtables (DHTs). Using DHTs  distributed hashtables (DHTs), this observation
90    is no longer true.
91    
92    Using DHTs
93  to resolve location-independent identifiers on the Web  to resolve location-independent identifiers on the Web
94  has been proposed by Balakrishnan et.al.  has been proposed by Balakrishnan et.al.
95  [balakrishnan03semanticfree-andalso-walfish03dns]_.  [balakrishnan03semanticfree-andalso-walfish03dns]_.

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