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<!--
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  * datafiles.html
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  *
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  *      Authors: Chad Berkley
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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: 2001 January 23
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  *      Version: 
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  *    File Info: '$ '
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  * 
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  * 
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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">Non-XML Data Files</p></td>
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      <td class="tablehead" colspan="2" align="right">
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        <a href="./replication.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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        <a href="./properties.html">Next</a>
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      </td>
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    </tr>
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  </table>
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  <p>Metacat has the capability of proxying a connection to a data file 
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  server.  This capability is provided through an abstract class called
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  DataFileUploadInterface.  Currently, there is a data file server implemented
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  for this interface that can store non-XML data files on the local UNIX
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  file system.  Theoretically, any file storage system could be proxied
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  through this interface.</p>
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  <P> <img alt="architecture diagram of the Metacat Data File Upload process" 
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           src="dataload.gif">  </p>
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  <b>Reasoning</b>
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  <p>Since Metacat has been designed as a metadata storage system for 
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  ecological data, there was a concern that data and metadata files were being
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  stored seperately and that users would find it impractical to have to use
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  two different systems to get their data and metadata.  This system also allows
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  users to specify <a href="./acontrol.html">access control</a> restraints on their
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  data files the same way that they are specified on the xml metadata files.</p>
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  <b>Data Download (GET)</b>
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  <p>Metacat Server can retrieve data files that are stored on Metacat
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     file system or in any other file system on Internet. <br>
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     Metacat stores data files in a directory under the servlet context.
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     It writes information about these data files in xml_documents just like
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     about any XML file. <br>
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     An example of HTTP request for download of data file on Metacat is shown below: </p>
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  <pre><i>http://server.domain.com/metacat?action=read&amp;docid=nceas.55</i></pre>
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  <p>An example of HTTP request for download of data file on Internet is shown below:</p>
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  <pre><i>http://server.domain.com/metacat?action=read&amp;docid=http://otherserver.domain.com/filename</i></pre>
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  <p>Note in <i>docid=http://otherserver.domain.com/filename</i> HTTP protocol is used,
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     i.e. currently for file download HTTP protocol is only supported.</p>
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  <p><b>Data Upload (PUT)</b></p>
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  <p>
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  The insertion and update process for a data file is the same as the 
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  insertion process for an <a href="metacatload.html">XML file</a>.
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  </p>
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  <br>
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  <a href="./replication.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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  <a href="./properties.html">Next</a>
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</BODY>
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