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berkley
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<!--
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* metacatread.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">Reading a Document
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from the Database</p></td>
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<td class="tablehead" colspan="2" align="right">
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<a href="./metacatquery.html">Back</a> | <a href="./metacattour.html">Home</a> |
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<a href="./saxparser.html">Next</a>
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</td>
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</tr>
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</table>
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<p>Metacat allows clients to read a document in several different ways,
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depending on how the client wants the document returned and how the client
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wants to specify the requested document. </p>
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<P> <img alt="architecture diagram of the Metacat read process"
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src="metadataread.gif"> </p>
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<p>The documents are requested by <b>docid</b> servlet parameter:
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<ul>
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<li> By docid alone as: <br>
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<i>docid=NCEAS.54</i></li>
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<li> By Metacat URL as: <br>
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<i>docid=metacat://server.domain.com/metacat?docid=NCEAS.54</i></li>
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<li> By HTTP URL: <br>
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<i>docid=http://otherserver.domain.com/filename</i></li>
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</ul>
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</p>
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<p>There are two different output formats that a client can request from
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Metacat: HTML or XML. This is specified by the <b>qformat</b> parameter. <br>
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If more than one document is requested, the qformat does not matter,
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instead the documents are zipped together and retrieved to the client. <br>
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When <b>abstractpath</b> parameter along with docid parameter is
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specified as a XPath expression of the location of abstract data within
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XML document, the abstract data only are read and retrieved in XML format.
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<p>For example, if a user wanted to request document NCEAS.54 and have it
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returned as HTML, the servlet call would look like this: <br>
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<i>http://server.domain.com/knb/servlet/metacat?action=read&qformat=html&docid=NCEAS.54</i>
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<br>
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Another way to request a document is by Metacat URL. the URL would look like: <br>
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<i>http://server.domain.com/knb/servlet/metacat?
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action=read&qformat=xml&docid=metacat://server.domain.com/metacat?docid=NCEAS.54</i>
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<br>
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Note that this url requests that the document be delivered in xml instead of html.
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</p>
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<p>
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Metacat URLs as in the second example become useful when more than one Metacat
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server is being run at one site or a bunch of sites are replicating between each
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other and you want to specify a document at a precise location.
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<!-- <a href="./packages.html">Package</a>
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files exclusively use Metacat URLs for document identification. -->
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</p>
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<br>
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<a href="./metacatquery.html">Back</a> | <a href="./metacattour.html">Home</a> |
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<a href="./saxparser.html">Next</a>
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</BODY>
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</HTML>
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