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<!--
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  * Metacatdb.html
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  *
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  *      Authors: Jivka Bojilova
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  *    Copyright: 2000 Regents of the University of California and the
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  *               National Center for Ecological Analysis and Synthesis
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  *  For Details: http://www.nceas.ucsb.edu/
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  *      Created: 2000 April 5
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  *      Version: 0.01
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  *    File Info: '$Id: metacatdb.html 881 2001-12-18 19:50:12Z berkley $'
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  * 
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  * October Meeting SDSC, 2000
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-->
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<HTML>
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<HEAD>
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<TITLE>Metacat</TITLE>
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<link rel="stylesheet" type="text/css" href="@docrooturl@default.css">
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</HEAD> 
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<BODY>
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  <table width="100%">
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    <tr>
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      <td class="tablehead" colspan="2"><p class="label">Metacat Database</p></td>
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      <td class="tablehead" colspan="2" align="right">
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        <a href="./metacat.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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        <a href="./metacatdom.html">Next</a>
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      </td>
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    </tr>
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  </table>
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  <P>Metacat's backend database stores the structure and data of any arbitrary 
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  XML document. The Metacat database uses the DOM 
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  approach to store XML documents as a hierarchy of nodes. All nodes are stored 
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  as records in database tables. The hierarchical relationship between the nodes 
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  is saved to preserve the structure of the documents.</p>
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  <p>The database Entity Relationship Diagram (ERD) currently looks like this:</p>
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  <img alt="Entity Relationship Diagram of the Metacat Database" src="metacatdb.gif">
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  <br><br>
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  <b>Table Descriptions</b>
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  <ul>
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    <li><b>xml_documents</b> contains document level information.  It
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    stands as a tie in to xml_nodes with the rootnodeid field.</li>
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    <li><b>xml_nodes</b> contains all of the data needed to recreate an
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    XML document that has been inserted into the system.  Each document's xml tree
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    is represented by the node pointers in the table.  </li>
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    <li><b>xml_index</b> contains indexing information for the paths in 
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    xml_nodes.  This is data that has been denormalized for performance reasons.  
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    xml_index allows the fast searching of paths within an xml document.</li>
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    <li><b>xml_revisions</b> contains the document information (including the 
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    rootnode pointer) to any document that has been deleted (either by an explicit
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    delete or by an update).  This ensures that a complete lineage of any document
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    is traced.</li>
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    <li><b>xml_replication</b> contains the list of Metacat servers that this
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    server replicates to or from.</li>
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    <li><b>xml_relation</b> contains any relation information inserted by a 
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    <a href="./packages.html">Package</a> document.</li>
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    <li><b>xml_access</b> contains all <a href="acontrol.html">Access Control List</a> (ACL) information 
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    relevent to a document.</li>
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    <li><b>xml_catalog</b>  contains catalog information that represents DTDs 
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    and XSL stylesheets that are registered with the system.</li>
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  </ul>
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  <br>
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  <a href="./metacat.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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  <a href="./metacatdom.html">Next</a>
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  </BODY>
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</HTML>
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