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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: '$Id$'
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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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