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<!--
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  * Metacatdom.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: metacatdom.html 2310 2004-09-21 09:01:22Z jones $'
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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">The Metacat DOM</p></td>
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      <td class="tablehead" colspan="2" align="right">
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        <a href="./metacatdb.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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        <a href="./clientapi.html">Next</a>
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      </td>
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    </tr>
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  </table>
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  <P>In the Metacat DOM implementation XML documents 
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  are disassembled into their composite nodes. All nodes are stored as records 
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  in the database tables. The structure of each XML document is preserved 
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  by saving the parent-child relationship between the nodes.
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    <ul>
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    <li> Each XML document in the Metacat database starts with one root node of 
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    type DOCUMENT. All other nodes in the document are its children. 
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    The document node can 
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    have multiple COMMENT or PI (processing instruction) nodes and only 
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    one ELEMENT node. The element node is the root node of the document and will
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    be pointed to by all of its children.
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    <li> Each node is described as a single record in the <i>xml_nodes</i> table. 
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    All nodes have a unique System ID (<i>nodeid</i>). Each node stores 
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    the ID of 
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    its direct parent (in <i>parentnodeid</i>), the ID of its documents root node 
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    (in <i>rootnodeid</i>) and its Document ID (<i>docid</i>).
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    <li> Document attributes (such as docid, doctype, etc.) are stored in 
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    the xml_documents table.
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    <li> Unimplemented DOM features:
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         <ul>
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         <li> Node types: Doctype, Entity, EntityReference, Notation.
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         <li> Persistant DOM interface. This would allow a DOM compliant 
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         editor to work with an xml document in the database as if it were
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         in memory.
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         <li>Object Oriented representation of each node.
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         </ul>
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    </ul>
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  <P> <img alt="Entity Relationship Diagram of the Metacat DOM"  src="metacatdom.jpg">
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  <br>
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  <a href="./metacatdb.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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  <a href="./clientapi.html">Next</a>
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</BODY>
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</HTML>
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