/[gzz]/manuscripts/pointers/article.rst
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revision 1.159 by benja, Thu Nov 6 14:48:09 2003 UTC revision 1.160 by benja, Thu Nov 6 14:52:33 2003 UTC
# Line 129  the current version of the tree. A node Line 129  the current version of the tree. A node
129  in the DHT will update a mapping if the update message  in the DHT will update a mapping if the update message
130  is signed with the appropriate key, and contains a timestamp  is signed with the appropriate key, and contains a timestamp
131  newer than that of the current version.  newer than that of the current version.
132    In CFS, version information is stored in the DHT, and only
133    as long as the publisher regularly requests it to be kept;
134    information about past versions isn't stored at all.
135    
136  In *OceanStore* [kubiatowicz00oceanstore]_,  In *OceanStore* [kubiatowicz00oceanstore]_,
137  an Internet-scale distributed data store that  an Internet-scale distributed data store that
# Line 146  OceanStore is unique among the versioned Line 149  OceanStore is unique among the versioned
149  in that it implements non-destructive updates,  in that it implements non-destructive updates,
150  allowing previous versions of documents to be accessed  allowing previous versions of documents to be accessed
151  (by using their old heartbeats).  (by using their old heartbeats).
152    In OceanStore, requesting a document's current version
153    depends on querying its primary replica; when the primary
154    replica ceases to function, the current version cannot be
155    determined any longer (for some applications, this only happens
156    30 seconds after the primary replica disappears).
157    
158  .. [#consistencytime] Many applications  .. [#consistencytime] Many applications
159     are believed to be able to cope with looser consistency     are believed to be able to cope with looser consistency
# Line 170  version ``n+1`` using an ``<img>`` link. Line 178  version ``n+1`` using an ``<img>`` link.
178  version ``n+1`` is actually inserted into the system; thus,  version ``n+1`` is actually inserted into the system; thus,
179  when the image does show up, the user knows that they should click  when the image does show up, the user knows that they should click
180  on it to get to a newer version of the document.  on it to get to a newer version of the document.
181    In Freenet, files only stay online as long as they are
182    requested regularly; keeping a copy on your harddisk
183    does not keep a page alive.
184    
185  Finally, a simplistic approach to P2P versioning  Finally, a simplistic approach to P2P versioning
186  is to have a centralized server keep track of the current version  is to have a centralized server keep track of the current version
# Line 181  This provides some of the efficiency adv Line 192  This provides some of the efficiency adv
192  However, there is still a single point of failure, and  However, there is still a single point of failure, and
193  links still break when pages move to a different directory  links still break when pages move to a different directory
194  or Web server.  or Web server.
   
 In a filesharing system, a file remains accessible  
 as long as there is a copy on any of the participating hosts.  
 None of the above versioning systems have this property.  
 In CFS, version information is stored in the DHT, and only  
 as long as the publisher regularly requests it to be kept.  
 In OceanStore, requesting a document's current version  
 depends on querying its primary replica; when the primary  
 replica ceases to function, the current version cannot be  
 determined any longer (for some applications, this only happens  
 30 seconds after the primary replica disappears).  
 In Freenet, files only  
 remain on-line as long as they are requested regularly in any case.  
195  In the Content-Addressable Web proposal, the situation  In the Content-Addressable Web proposal, the situation
196  is the same as on the current Web.  regarding versioning is the same as on the current Web.
197    
198    In conclusion, a filesharing system, a file remains accessible
199    as long as there is a copy on any of the participating hosts;
200    none of the above versioning systems have this property.
201    
202  Thus, in these systems, when the original publisher loses interest  Thus, in these systems, when the original publisher loses interest
203  and stops publishing a page, it disappears, even if  and stops publishing a page, it disappears, even if

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