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  * harvester.html
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  *      Authors: Duane Costa
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  *    Copyright: 2004 Regents of the University of California and the
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  *               National Center for Ecological Analysis and Synthesis,
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  *               and the University of New Mexico.
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  *  For Details: http://www.nceas.ucsb.edu/
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  *      Created: 2004 April 9
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<HTML>
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<HEAD>
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<TITLE>Metacat Harvester</TITLE>
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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">
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        <p class="label">Metacat Harvester</p>
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      </td>
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      <td class="tablehead" colspan="2" align="right">
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        <a href="./properties.html">Back</a> |
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        <a href="./metacattour.html">Home</a> |
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        <a href="./unimplem.html">Next</a>
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      </td>
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    </tr>
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  </table>
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  <h4>Introduction</h4>
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The Metacat Harvester (henceforth referred to as "Harvester") is a
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program that automates the retrieval of EML documents from one or more sites
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and their subsequent upload (insert or update) to Metacat. Harvester uses pull
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technology to retrieve and upload documents to Metacat on a regularly
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scheduled basis.
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<P>
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Although Harvester is included with a Metacat installation (beginning with
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Metacat version 1.4.0), it is an extention to Metacat's functionality
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that may be used optionally.
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</P>
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  <h4>Definitions</h4>
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The following table defines a number of terms that are useful in discussing
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Harvester and its features.
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  <br><br>
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  <table border="1">
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    <tr>
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      <td><b>Term</b></td>
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      <td><b>Definition</b></td>
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    </tr>
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    <tr>
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      <td>Harvester</td>
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      <td>The Harvester program, a Java application that is bundled with the
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          Metacat distribution. When a user installs Metacat on a system,
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          the Harvester program is automatically included in the
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          installation.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvester Administrator</td>
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      <td>The individual who installs and manages Harvester. Typically, this
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          would be the same individual who installs and manages Metacat at a
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          given installation.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvest Site</td>
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      <td>A location from which Harvester can retrieve EML documents. A given
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          Harvester can retrieve documents from any number of different
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          Harvest Sites.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvest</td>
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      <td>The act (by Harvester) of visiting a Harvest Site, retrieving a
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          number of EML documents, and inserting or updating the documents to
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          Metacat.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvest List</td>
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      <td>An XML document that lists a set of EML documents to be harvested. The
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          Harvest List must conform to an XML Schema,
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          <a href="../../lib/harvester/harvestList.xsd">harvestList.xsd</a>.
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      </td>
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    </tr>
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    <tr>
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      <td>Site Contact</td>
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      <td>The individual at a particular Harvest Site who registers with
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          Harvester, composes a Harvest List, and periodically prepares
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          the site's EML documents for retrieval and upload to Metacat.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvest List URL</td>
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      <td>A URL to the Harvest List, as specified by the Site Contact.
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          Each Harvest Site corresponds to a Harvest List URL. Harvester
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          uses the URL to locate and read a site's Harvest List.
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      </td>
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    </tr>
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    <tr>
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      <td>Document URL</td>
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      <td>A URL to an EML document, as specified in the Harvest List.
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          The Harvest List may contain any number of Document URLs. Each
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          Document URL provides a locator to a document to be harvested.
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      </td>
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    </tr>
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    <tr>
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      <td>Harvester Registration Page</td>
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      <td>A web page that provides a means for a Site Contact
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          to register with Harvester to schedule regular harvests from the
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          site. Registration involves logging in and then specifying various
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          settings for the Harvest Site, such as the Harvest List URL, the
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          harvest frequency, and the email address of the Site Contact.
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      </td>
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    </tr>
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  </table>
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  <h4>Managing Harvester</h4>
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  Harvester is managed by the Harvester Administrator. Typically, the same
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  individual who manages a Metacat server would also act as the Harvester
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  Administrator. The responsibilities of the Harvester Administrator include:
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    <ul>
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      <li><a href="#Configuring Harvester">Configuring Harvester</a></li>
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      <li><a href="#Running Harvester">Running Harvester</a></li>
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      <li><a href="#Reviewing Harvester">Reviewing Harvester reports to
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      the Harvester Administrator</a></li>
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    </ul>
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  <h5><a name="Configuring Harvester">Configuring Harvester</a></h5>
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  <p>Harvester must be configured to interact with a working Metacat
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     installation. Thus, a Metacat installation that has been properly
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     configured and installed is a pre-requisite to running Harvester.
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     Additionally, Harvester has a number of settable properties that
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     control its behavior. All Harvester configuration information is managed
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     in a single file,
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     <a href=../../lib/harvester/harvester.properties>harvester.properties</a>,
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     located at:
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  <pre>      METACAT_HOME/lib/harvester/harvester.properties</pre>
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     where METACAT_HOME is the top-level directory that Metacat is
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     installed in.
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  </p>
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  <p>The Harvester Administrator should edit
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     <a href=../../lib/harvester/harvester.properties>harvester.properties</a>,
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     setting appropriate values for the Metacat URL, database driver,
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     database connection, and other settings. The
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     following table is a summary of each property and its function.
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  </p>
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  <table border="1">
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    <tr>
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      <td><b>Property</b></td>
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      <td><b>Description</b></td>
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      <td><b>Possible or default value</b></td>
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    </tr>
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    <tr>
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      <td>connectToMetacat</td>
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      <td>This property determines whether Harvester should connect to
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          Metacat to upload documents. It should be set to <code>true</code>
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          under most circumstances. Setting this property to <code>false</code>
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          can be useful for testing whether Harvester is able to retrieve
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          documents from a site without actually connecting to Metacat to
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          upload the documents.</td>
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      <td><code>true</code> | <code>false</code><br>
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          Default: <code>true</code>
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    </tr>
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    <tr>
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      <td>dbDriver</td>
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      <td>The JDBC driver to be used to access the backend database. This
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          setting should match the value of the dbDriver property as set
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          in the <a href=../../build.xml>build.xml</a> file as appropriate
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          to the database being used (Oracle, PostgreSQL, or SQL Server).
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      </td>
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      <td>Examples:<br>
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          <code>oracle.jdbc.driver.OracleDriver</code><br>
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          <code>org.postgresql.Driver</code><br>
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          <code>com.microsoft.jdbc.sqlserver.SQLServerDriver</code>
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      </td>
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    </tr>
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    <tr>
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      <td>defaultDB</td>
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      <td>The JDBC connection string that Metacat uses to connect to the
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          backend database. This setting should match the value of
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          the <code>jdbc-connect</code> property as set in the
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          <a href=../../build.properties>build.properties</a>
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          file in the associated Metacat installation.</td>
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      <td>Example:<br>
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          <code>jdbc:oracle:thin:@server.domain.com:1521:Metacat</code></td>
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    </tr>
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    <tr>
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      <td>delay</td>
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      <td>The number of hours that Harvester will wait before beginning its
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          first harvest. For example, if Harvester is run at  1:00 p.m., and
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          the delay is set to 12, Harvester will begin its first harvest at
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          1:00 a.m.</td>
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      <td>Default: 0</td>
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    </tr>
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    <tr>
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      <td>harvesterAdministrator</td>
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      <td>The email address of the Harvester Administrator. Harvester will
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          send email reports to this address after every harvest.
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      </td>
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      <td>An email address</td>
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    </tr>
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    <tr>
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      <td>logPeriod</td>
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      <td>The number of days that Harvester should retain log entries of harvest
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          operations in the database. Harvester log entries record information
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          such as which documents were harvested, from which sites, and
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          whether any errors were encountered during the harvest. Log entries
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          older than <code>logPeriod</code> number of days are purged from the
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          database at the end of each harvest.</td>
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      <td>Default: 90</td>
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    </tr>
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    <tr>
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      <td>maxHarvests</td>
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      <td>The maximum number of harvests that Harvester should execute before
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          shutting down. When the Harvester program is executed, it will
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          continue running until it has executed <code>maxHarvests</code>
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          number of harvests and then the program will terminate.</td>
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      <td>Default: 30</td>
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    </tr>
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    <tr>
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      <td>metacatURL</td>
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      <td>The URL of the Metacat servlet to which Harvester should connect
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          for uploading documents.</td>
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      <td>Example:<br>
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               http://somehost.institution.edu:8080/knb/servlet/metacat</td>
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    </tr>
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    <tr>
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      <td>password</td>
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      <td>The password that Harvester uses to access the backend database.
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          This setting should match the value of the <code>password</code>
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          property as set in the
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          <a href=../../build.properties>build.properties</a>
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          file in the associated Metacat installation.
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      </td>
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      <td>&nbsp;</td>
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    </tr>
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    <tr>
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      <td>period</td>
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      <td>The number of hours between harvests. Harvester will run a new
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          harvest every <code>period</code> number of hours, until the
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          <code>maxHarvests</code> number of harvests have been run.</td>
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      <td>Default: 24</td>
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    </tr>
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    <tr>
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      <td>smtpServer</td>
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      <td>The SMTP server that Harvester uses for sending email messages
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          to the Harvester Administrator and to Site Contacts.</td>
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      <td>A host name, for example: <code>somehost.institution.edu</code>
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          <br><br>
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          Default: <code>localhost</code>
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          <br><br>
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          Note that the default value will only work if the Harvester
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          host machine has been configured as a SMTP server.
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      </td>
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    </tr>
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    <tr>
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      <td>user</td>
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      <td>The username that Metacat uses to access the backend database.
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          This setting should match the <code>user</code> value as set in the
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          <a href=../../build.properties>build.properties</a>
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          file in the associated Metacat installation.
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      </td>
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      <td>&nbsp;</td>
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    </tr>
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    <tr>
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      <td>Harvester Operation Properties (GetDocError, GetDocSuccess, etc.)</td>
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      <td>This group of properties is used by Harvester to report information
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          about the operations it performs for inclusion in log
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          entries and email messages. Under most circumstances the values
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          of these properties should not be modified.</td>
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      <td>&nbsp;</td>
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    </tr>
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  </table>
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  <br>
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  <h5><a name="Running Harvester">Running Harvester</a></h5>
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  After Harvester has been appropriately
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  <a href="#Configuring Harvester">configured</a>,
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  it can be run as follows:
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  <ol>
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  <li>Open a system command window or terminal window.</li>
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  <li>Set the METACAT_HOME environment variable to the value of the Metacat
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      installation directory. Some examples follow:
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      <ul>
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        <li>On Windows:
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        <pre>set METACAT_HOME=C:\somePath\metacat</pre></li>
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        <li>On Linux/Unix (bash shell):
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        <pre>export METACAT_HOME=/home/somePath/metacat</pre></li>
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      </ul>
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  <li>cd to the following directory:
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      <ul>
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        <li>On Windows:
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        <pre>cd %METACAT_HOME%\lib\harvester</pre></li>
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        <li>On Linux/Unix:
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        <pre>cd $METACAT_HOME/lib/harvester</pre></li>
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      </ul>
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  <li>Run the appropriate Harvester shell script, as determined by the
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      operating system:
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      <ul>
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        <li>On Windows:
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        <pre>runHarvester.bat</pre></li>
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        <li>On Linux/Unix:
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        <pre>sh runHarvester.sh</pre></li>
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      </ul>
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  </li>
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  </ol>
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  <p>The Harvester application will start executing. It will begin its first
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  harvest after <code><b>delay</b></code> number of hours (as specified in the
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  <a href=../../lib/harvester/harvester.properties>harvester.properties</a>
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  file). The application will continue running a new harvest every
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  <code><b>period</b></code> number of hours until a <code><b>maxHarvests</b></code>
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  number of harvests have been completed.
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  </p>
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  <h5><a name="Reviewing Harvester">
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  Reviewing Harvester Reports to the Harvester Administrator</a></h5>
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  <P>
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  After every harvest, Harvester will send an email report to the Harvester
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  Administrator detailing the operations that were performed during the
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  harvest. The report will contain information about each of the Harvest Sites
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  that were harvested from, such as which EML documents were
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  harvested and whether any errors were encountered.
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  </P>
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  <p>
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  The harvest report will contain a list of log entries, where each log entry
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  describes an operation that was performed by Harvester. Log entries that
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  show a status value of 1 indicate that an error occurred during the
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  operation, while those that show a status value of 0 indicate that the
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  operation was completed successfully.
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  </p>
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  <P>The Harvester Administrator should review the report, paying particularly
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  close attention to any errors that are reported and to the accompanying error
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  messages that are displayed. When errors are reported at
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  a particular site, the Harvester Administrator should contact the Site
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  Contact to determine the source of the error and its resolution. See
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  <a href=#Reviewing>Reviewing Harvester Reports to the Site Contact</a> for a
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  description of common sources of errors at a Harvest Site.
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  </P>
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  <p>Errors that are independent of a particular site may indicate a problem
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  with Harvester itself, Metacat, or the database connection. Refer to the
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  error message to determine the source of the error and its resolution.
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  </p>
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  <h4>Managing a Harvest Site</h4>
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  A Harvest Site is managed by a Site Contact.
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  The responsibilities of a Site Contact fall into the following categories:
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    <ul>
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      <li><a href=#Registering>Registering with Harvester</a></li>
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      <li><a href=#Composing>Composing a Harvest List</a></li>
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      <li><a href=#Preparing>Preparing EML Documents for harvest</a></li>
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      <li><a href=#Reviewing>Reviewing Harvester reports to the Site Contact</a></li>
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    </ul>
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    <h5><a name="Registering">Registering with Harvester</a></h5>
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  <p>
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  A Site Contact registers a site with Harvester by logging in to the
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  Harvester Registration page and entering several items of information
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  that Harvester needs to know about the site.
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  </p>
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  <ol>
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    <li>Logging in to the Harvester Registration Page
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  <p>
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  The Harvester Registration page is accessed from Metacat. For example, if
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  the Metacat server that you wish to register with resides at the following
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  URL:
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  <pre>  http://somehost.somelocation.edu:8080/knb/index.jsp</pre>
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  then the Harvester Registration page would be accessed at:
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  <pre>  http://somehost.somelocation.edu:8080/knb/style/skins/dev/harvesterRegistrationLogin.html</pre>
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  </p>
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  <p>
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  After bringing up this page in your browser, login to your Metacat account
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  by entering your username and password.
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  The username should include the full LDAP specification, for example:
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  <pre>
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  Username:   uid=jdoe,o=lter,dc=ecoinformatics,dc=org
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  Password:   *******
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  </pre>
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  In some cases, a Site Contact may need to login to an anonymous account
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  rather than his or her personal account. For example, a LTER Information
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  Manager may need to login to a dedicated account, named with a three-letter
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  acronym, that has been set up for the LTER site. For example:
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  <pre>
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  Username:   uid=GCE,o=lter,dc=ecoinformatics,dc=org
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  Password:   *******
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  </pre>
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  is the account login that would be used by the LTER Information Mangager
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  at the GCE (Georgia Coastal Ecosystems) site.
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  </p>
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    </li>
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    <li>Registering with Harvester
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  <p>
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  After logging in, you will be presented with a web form that prompts you
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  to enter information about your site and how often you want to schedule
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  harvests at your site. For example:
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  </p>
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  <pre>
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  Email address:            myname@institution.edu
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  Harvest List URL:         http://somehost.institution.edu/~myname/harvestList.xml
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  Harvest Frequency (1-99): 2
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  Unit:                     ( ) day(s)    (*) week(s)   ( ) month(s)
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  </pre>
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  After values have been entered for each of these fields, click the Register
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  button to register your site with Harvester.
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  </p>
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  <P>
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  In the example shown above, Harvester will attempt to harvest documents from
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  the site once every 2 weeks, it will access the site's Harvest List at URL
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  "http://somehost.institution.edu/~myname/harvestList.xml", and it will send
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  email reports to the Site Contact at email address "myname@institution.edu".
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  </P>
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    </li>
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    <li>Unregistering with Harvester
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  <p>
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  At any time after you have registered with Harvester, you may discontinue
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  harvests at your site by unregistering. Simply login as described above and
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  then click the Unregister button. After doing so, Harvester will discontinue
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  harvests at the site.
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  </p>
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    </li>
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  </ol>
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  <h5><a name="Composing">Composing a Harvest List</a></h5>
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  <p>
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  A Harvest List is an XML file that holds a list of EML documents to be
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  harvested. For each EML document in the list, the following information
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  must be specified:
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  <ul>
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    <li><code>docid</code>, which consists of the:
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      <ul>
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        <li><code>scope</code>, e.g. "demoDocument". The scope is an identifier
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            that indicates which group of documents this document belongs to.
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        </li>
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        <li><code>identifier</code>, e.g. "1". The identifier is a number that
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            uniquely identifies this document within the scope.
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        </li>
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        <li><code>revision</code>, e.g. "5". The revision is a number that
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            indicates the current revision of this document.
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        </li>
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      </ul>
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    </li>
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    <li><code>documentType</code>, e.g. "eml://ecoinformatics.org/eml-2.0.0".
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        The documentType identifies the document as an EML document.</li>
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    <li><code>documentURL</code>, e.g. "http://www.lternet.edu/~dcosta/document1.xml".
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        The documentURL specifies a place where Harvester can locate
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        and retrieve the document via HTTP.</li>
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  </ul>
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  </p>
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  <p>
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  The contents of a Harvest List XML file must conform to a particular
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  XML Schema, as defined in file <a href="../../lib/harvester/harvestList.xsd">
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  harvestList.xsd</a>. The contents of a valid Harvest List
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  can best be illustrated by example. The sample Harvest List
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  below contains two &lt;<code>document</code>&gt; elements that specify the
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  information that Harvester needs to retrieve a pair of EML documents and
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  upload them to Metacat:
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  <pre>
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&lt;?xml version="1.0" encoding="UTF-8" ?&gt;
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&lt;hrv:harvestList xmlns:hrv="eml://ecoinformatics.org/harvestList" &gt;
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    &lt;document&gt;
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        &lt;docid&gt;
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            &lt;scope&gt;demoDocument&lt;/scope&gt;
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            &lt;identifier&gt;1&lt;/identifier&gt;
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            &lt;revision&gt;5&lt;/revision&gt;
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        &lt;/docid&gt;
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        &lt;documentType&gt;eml://ecoinformatics.org/eml-2.0.0&lt;/documentType&gt;
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        &lt;documentURL&gt;http://www.lternet.edu/~dcosta/document1.xml&lt;/documentURL&gt;
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    &lt;/document&gt;
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    &lt;document&gt;
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        &lt;docid&gt;
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            &lt;scope&gt;demoDocument&lt;/scope&gt;
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            &lt;identifier&gt;2&lt;/identifier&gt;
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            &lt;revision&gt;1&lt;/revision&gt;
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        &lt;/docid&gt;
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        &lt;documentType&gt;eml://ecoinformatics.org/eml-2.0.0&lt;/documentType&gt;
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        &lt;documentURL&gt;http://www.lternet.edu/~dcosta/document2.xml&lt;/documentURL&gt;
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    &lt;/document&gt;
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&lt;/hrv:harvestList&gt;
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  </pre>
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  <p>
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  After editing the Harvest List, ensure that the Harvest List XML file resides
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  at the appropriate location on disk as specified by the URL that was entered
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  during the <a href=#Registering>registration</a> process.
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  </p>
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    <h5><a name="Preparing">Preparing EML Documents for harvest</a></h5>
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  <p>
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  To prepare a set of EML documents for harvest, ensure that the following is
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  true for each document:
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  <ul>
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    <li>The document contains valid EML</li>
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    <li>The document is specified in a &lt;document&gt; element in the
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        site's Harvest List, as described above</li>
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    <li>The file resides at the appropriate location on disk as specified
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        by its URL in the Harvest List</li>
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  </ul>
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  </p>
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    <h5><a name="Reviewing" >Reviewing Harvester Reports to the Site Contact</a></h5>
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  <P>
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  After every scheduled harvest that takes place at a particular Harvest
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  Site, Harvester will send an email report to the Site Contact detailing the
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  operations that were performed during the harvest.
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  The report will contain information about the operations that were
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  performed by Harvester at that site, such as
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  which EML documents were harvested and whether any errors were encountered.
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  </P>
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  <P>
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  The Site Contact should review the report, paying particularly
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  close attention to any errors that are reported. Errors are indicated
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  by operations that display a status value of 1, while operations that
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  display a status value of 0 indicate that the operation completed
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  successfully.
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  </P>
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  <p>
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  When errors are reported,
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  the Site Contact should try to determine whether the source of the error
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  is something that can be corrected at the site. Common causes of errors
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  might be:
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  <ul>
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    <li>A document URL specified in the Harvest List does not match
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        the location of the actual EML file on the disk</li>
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    <li>The Harvest List does not contain valid XML as specified in
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        the <a href=../../lib/harvester/harvestList.xsd>harvestList.xsd</a> schema</li>
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    <li>The URL to the Harvest List that was specified during
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        registration with Harvester does not match the actual location of
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        the Harvest List on the disk</li>
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    <li>An EML document that Harvester attempted to upload to Metacat does
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        not contain valid EML</li>
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  </ul>
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  </P>
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  <p>
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  If the Site Contact is unable to determine the cause of the error and its
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  resolution, he or she should contact the Harvester Administrator for assistance.
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  </p>
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