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<!--
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  * metacatquery.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: metacatquery.html 3775 2008-03-21 20:31:22Z tao $'
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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">Queries and Results</p></td>
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      <td class="tablehead" colspan="2" align="right">
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        <a href="./metacatload.html">Back</a> | <a href="./metacattour.html">Home</a> | 
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        <a href="./metacatread.html">Next</a>
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      </td>
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    </tr>
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  </table>
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  <P>The Metacat Server provides 
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  an interface for searching of metadata stored in the Metacat database.
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  <P> <img alt="architecture diagram of a Metacat query" src="metadataquery.gif">
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  <br><br><b>Steps to perform a query in Metacat</b>
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  <ol>
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    <li>A pathquery document is created from the search criteria provided through
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    the servlet parameters.</li>  
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    <li>This pathquery document is sent to DBQuery where it 
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    is processed and translated into SQL statements.</li>
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    <li>The SQL statements are executed against the database and the resultsets
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    are translated into an xml document of doctype "resultset".</li>
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    <li>The resultset document is either returned directly to the client as XML
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    or is transformed through XSLT and returned as HTML.</li>
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  </ol>
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  <b>The Pathquery Document</b>
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  <pre>
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   &lt;pathquery version="1.0"&gt;
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      &lt;meta_file_id&gt;unspecified&lt;/meta_file_id&gt;
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      &lt;querytitle&gt;unspecified&lt;/querytitle&gt;
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      &lt;returnfield&gt;dataset/title&lt;/returnfield&gt;
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      &lt;returnfield&gt;keyword&lt;/returnfield&gt;
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      &lt;returnfield&gt;originator/individualName/surName&lt;/returnfield&gt;
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      &lt;returndoctype&gt;eml://ecoinformatics.org/eml-2.0.1&lt;/returndoctype&gt;
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      &lt;returndoctype&gt;eml://ecoinformatics.org/eml-2.0.0&lt;/returndoctype&gt;
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      &lt;querygroup operator="UNION"&gt;
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        &lt;queryterm casesensitive="false" searchmode="contains"&gt;
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          &lt;value&gt;Datos&lt;/value&gt;
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          &lt;pathexpr&gt;dataset/title&lt;/pathexpr&gt;
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        &lt;/queryterm&gt;
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        &lt;queryterm casesensitive="false" searchmode="contains"&gt;
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          &lt;value&gt;plant&lt;/value&gt;
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          &lt;pathexpr&gt;keyword&lt;/pathexpr&gt;
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        &lt;/queryterm&gt;
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      &lt;/querygroup&gt;
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  &lt;/pathquery&gt;
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  </pre>
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  <p>The pathquery document was designed to be flexible enough to query specific
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  fields of any XML document.  It also allows the client to specify which fields
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  from a returned document are returned in the initial resultset.  Each
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  &lt;returnfield&gt; parameter specifies a field which the DB will return
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  for any query hit.  The returndoctype fields allows the client to limit the 
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  type of documents to be returned.  If no returndoctype element , all document types are returned.
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  A &lt;querygroup&gt; creates an AND or an OR statement of the &lt;queryterm&gt;s
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  in the group.  The operator can be UNION or INTERSECT.  A &lt;queryterm&gt;
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  defines the actual field against which the query is being performed.  The value
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  of the queryterm that we are quering for is encased in &lt;value&gt; tags.
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  The &lt;pathexpr&gt; tag specifies an exact path to which you want to restrict
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  the search.  A &lt;pathexpr&gt; tag which contains the keyword returndoc is 
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  a special case which is discussed in <a href="./packages.html">Packages and 
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  Relations</a>.</p><br>
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  <b>The Resultset Document</b><br>
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  <p>When the pathquery document is submitted and processed, Metacat returns
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  another XML document called a resultset document.<p>
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  <pre>
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      &lt;resultset&gt;
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        &lt;query&gt;
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          &lt;pathquery version="1.0"&gt;
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            &lt;meta_file_id&gt;unspecified&lt;/meta_file_id&gt;
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            &lt;querytitle&gt;unspecified&lt;/querytitle&gt;
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            &lt;returnfield&gt;dataset/title&lt;/returnfield&gt;
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            &lt;returnfield&gt;keyword&lt;/returnfield&gt;
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            &lt;returnfield&gt;originator/individualName/surName&lt;/returnfield&gt;
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            &lt;returndoctype&gt;eml://ecoinformatics.org/eml-2.0.1&lt;/returndoctype&gt;
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            &lt;returndoctype&gt;eml://ecoinformatics.org/eml-2.0.0&lt;/returndoctype&gt;
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            &lt;querygroup operator="UNION"&gt;
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                  &lt;queryterm casesensitive="false" searchmode="contains"&gt;
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                      &lt;value&gt;Datos&lt;/value&gt;
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                      &lt;pathexpr&gt;dataset/title&lt;/pathexpr&gt;
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                  &lt;/queryterm&gt;
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                  &lt;queryterm casesensitive="false" searchmode="contains"&gt;
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                     &lt;value&gt;plant&lt;/value&gt;
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                     &lt;pathexpr&gt;keyword&lt;/pathexpr&gt;
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                  &lt;/queryterm&gt;
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           &lt;/querygroup&gt;
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         &lt;/pathquery&gt;
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        &lt;/query&gt;  
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        &lt;document&gt;
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          &lt;docid&gt;nceas.44.1&lt;/docid&gt;
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          &lt;docname&gt;resource&lt;/docname&gt;
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          &lt;doctype&gt;eml://ecoinformatics.org/eml-2.0.1&lt;/doctype&gt;
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          &lt;createdate&gt;2001-01-12 16:12:06.0&lt;/createdate&gt;
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          &lt;updatedate&gt;2001-01-12 16:12:06.0&lt;/updatedate&gt;
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          &lt;param name="dataset/title"&gt;Datos Meteorologicos&lt;/param&gt;
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          &lt;param name="keyword"&gt;intertidal&lt;/param&gt;
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          &lt;param name="originator/individualName/surName"&gt;Smith&lt;/param&gt;
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        &lt;/document&gt;  
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        &lt;document&gt;
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          &lt;docid&gt;nceas.42.1&lt;/docid&gt;
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          &lt;docname&gt;resource&lt;/docname&gt;
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          &lt;doctype&gt;eml://ecoinformatics.org/eml-2.0.1&lt;/doctype&gt;
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          &lt;createdate&gt;2001-01-12 16:11:31.0&lt;/createdate&gt;
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          &lt;updatedate&gt;2001-01-12 16:11:31.0&lt;/updatedate&gt;
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          &lt;param name="dataset/title"&gt;Ocean Surface Temperature&lt;/param&gt;
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          &lt;param name="keyword"&gt;Plant&lt;/param&gt;
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          &lt;param name="originator/individualName/surName"&gt;Henry&lt;/param&gt;   
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       &lt;/document&gt;
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      .....  
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      &lt;/resultset&gt;
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  </pre>
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  <p>The first element in the resultset is &lt;query&gt;.  Its content is just 
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  the pathquery document.  The resultset always returns 
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  the pathquery document that created it in the &lt;query&gt; tag.  The next
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  major tag is &lt;document&gt;.  Each XML document returned by the query
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  is represented by a &lt;document&gt; tag.  The default document information returned
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  is docid, docname, doctype, doctitle, createdate and  
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  updatedate.  The param tags are present if the document found contained
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  the returnfield chosen in the pathquery document.  The name attribute of the
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  param tag is the full path to the node specified by the returnfield. <p>
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