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revision 1.177 by hemppah, Mon Mar 24 12:31:59 2003 UTC revision 1.178 by hemppah, Mon Mar 24 14:07:50 2003 UTC
# Line 1592  which is an essential part of Fenfire's Line 1592  which is an essential part of Fenfire's
1592    
1593  The Fenfire project \cite{fenfireurl} is an effort to build a location transparent, hyperstructured desktop  The Fenfire project \cite{fenfireurl} is an effort to build a location transparent, hyperstructured desktop
1594  environment. By location transparent, we mean concealing the heterogeneous and distributed nature of the system  environment. By location transparent, we mean concealing the heterogeneous and distributed nature of the system
1595  so that it appears to the end user like one system and by hyperstructured system,  so that it appears to the end user like one system and by hyperstructured system
1596  we mean a system in which data can be associated with other data arbitrarly. Fenfire uses xanalogical storage model  a system in which data can be associated with other data arbitrarly. Fenfire uses xanalogical storage model
1597  \cite{ted-xu-model} as a basis for hyperstructured media. Each data item in the Fenfire system has a globally unique  \cite{ted-xu-model} as a basis for hyperstructured media. Each data item in the Fenfire system has a globally unique
1598  identifier. This property should allow making references between \emph{any}  identifier. This property should allow making references between \emph{any}
1599  data easier and more seamlessly interoperating than in other systems. For location transparency in the Fenfire system,  data easier and more seamlessly interoperating than in other systems. For location transparency in the Fenfire system,
# Line 1620  in the Fenfire system. Line 1620  in the Fenfire system.
1620  \section{Xanalogical storage model}  \section{Xanalogical storage model}
1621    
1622  Xanalogical storage model \cite{nelson99xanalogicalneeded} is a different kind of model for  Xanalogical storage model \cite{nelson99xanalogicalneeded} is a different kind of model for
1623  presenting data and relationships between data. While in the World Wide Web links are  presenting data and relationships between data. \emph{Enfilade},
1624    can be considered as a mutable ''virtual file'' (or part of one), which is a list
1625    of fluid media content. Fluid media is the smallest units of data in xanalogical storage
1626    model. \emph{Transclusion} is an inclusion in
1627    enfilade of contents already used in another enfilade. With the transclusion, a system
1628    implementing xanalogical storage model is able to show all data content that share the same
1629    fluid media with current data content (e.g., all documents in a system containing a specific
1630    document's text).
1631    
1632    While in the World Wide Web links are
1633  between \emph{documents}, in xanalogical storage model links are between individual  between \emph{documents}, in xanalogical storage model links are between individual
1634  \emph{characters}. Each character in xanalogical storage model has a  \emph{characters}. Figure \ref{fig:xanalogical_model}
 permanent, globally unique identifier. For instance, let's consider the following  
 scenario: ''the character 'D' typed by Janne Kujala on 10/8/97 8:37:18''. In this  
 example, when character 'D' is first typed in, xanalogical storage model  
 acquires a permanent identifier for that character and retains it when the character  
 is copied to different document. Thus, the identifier distinguishes the character from  
 all similar characters typed in independently\footnote{Xanalogical storage model  
 is not limited to text. It can support arbitrary data, e.g., pixels of picture or  
 frames of video.}. The connectivity in xanalogical storage model between data content  
 is more substantial than in other models; a link is shown between any two data contents  
 containing a specific \emph{fluid media unit} (e.g., a character) that the link connects.  
 In practice, however, xanalogical storage model uses \emph{spans}, ranges of consecutive  
 fluid media units to perform storage operations. This is done for better performance as  
 doing expensive operations for every fluid media unit is not efficient. Xanalogical  
 storage model stores fluid media units to append-only \emph{scrolls}.  
   
 An \emph{enfilade} can be considered as a ''virtual file'' (or part of one), which is a list  
 of fluid media content. In xanalogical storage model, links between content are external  
 and bidirectional. Xanalogical link is an \emph{association} of two enfilades, such as an  
 annotation to a specific part of a another document. \emph{Transclusion} is an inclusion in  
 enfilade of contents already used in another enfilade, i.e., current fluid media is copied into  
 different data content. By using this mechanism, a system implementing xanalogical storage model  
 is able to show all data content that share the same fluid media with current data content  
 (e.g., all documents containing current document's text). Figure \ref{fig:xanalogical_model}  
1635  illustrates xanalogical storage model with documents, text and characters.  illustrates xanalogical storage model with documents, text and characters.
1636    Links between data are external
1637    and bidirectional. A link is shown between any two data contents
1638    containing a specific \emph{fluid media unit} (e.g., a character) that the link connects.
1639    Each fluid media unit in xanalogical storage model has a
1640    permanent, globally unique identifier\footnote{Xanalogical storage model
1641    is not limited to text. It can support arbitrary data, e.g., pixels of picture or
1642    frames of video.}. For instance, let's consider the following
1643    example, presented first time in \cite{lukka02freenetguids}: ''the character 'D'
1644    typed by Janne Kujala on 10/8/97 8:37:18''. When character
1645    'D' is first typed in, xanalogical storage model
1646    creates a permanent globally identifier for that character
1647    and retains it when the character is copied to different document. In practice, xanalogical
1648    storage model uses \emph{spans}, ranges of consecutive
1649    fluid media units to perform storage operations.
1650    
1651  \begin{figure}  \begin{figure}
1652  \centering  \centering

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