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139 lines
5.4 KiB
HTML
139 lines
5.4 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
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<html>
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<head>
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<title>DSpace System
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Documentation: Architecture</title>
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<link rel="StyleSheet" href="style.css" type="text/css">
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<meta http-equiv="Content-Type"
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content="text/html; charset=iso-8859-1">
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</head>
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<body>
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<h1>DSpace
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System Documentation: Architecture</h1>
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<p><a href="index.html">Back to contents</a></p>
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<h2><a name="overview">Overview</a></h2>
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<p>The DSpace system is organized
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into three layers, each of which
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consists of a number of components.</p>
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<p class="figure"><img src="image/architecture-600x450.gif"
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alt="Application Layer, Business Logic Layer, Storage Layer"></p>
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<p class="caption">DSpace
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System Architecture</p>
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<p>The storage layer is
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responsible for physical storage of metadata
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and content. The business logic layer deals with managing the content
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of the archive, users of the archive (e-people), authorization, and
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workflow. The application layer contains components that communicate
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with the world outside of the individual DSpace installation, for
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example the Web user interface and the <a
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href="http://www.openarchives.org/">Open Archives
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Initiative</a>
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protocol for metadata harvesting service.</p>
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<p>Each layer only invokes the
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layer below it; the application layer
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may not used the storage layer directly, for example. Each component in
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the storage and business logic layers has a defined public API. The
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union of the APIs of those components are referred to as the Storage
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API (in the case of the storage layer) and the DSpace Public API (in
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the case of the business logic layer). These APIs are in-process Java
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classes, objects and methods.</p>
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<p>It is important to note that
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each layer is <em>trusted</em>.
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Although the logic for <em>authorising
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actions</em> is in the business
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logic layer, the system relies on individual applications in the
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application layer to correctly and securely <em>authenticate</em>
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e-people. If a 'hostile' or insecure application were allowed to invoke
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the Public API directly, it could very easily perform actions as any
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e-person in the system.</p>
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<p>The reason for this design
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choice is that authentication methods
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will vary widely between different applications, so it makes sense to
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leave the logic and responsibility for that in these applications.</p>
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<p>The source code is organized to
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cohere very strictly to this
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three-layer architecture. Also, only methods in a component's public
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API are given the <code>public</code>
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access level. This means that
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the Java compiler helps ensure that the source code conforms to the
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architecture.</p>
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<table>
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<caption>Source Code Packages</caption> <tbody>
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<tr>
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<th>Packages within</th>
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<th>Correspond to components
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in</th>
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</tr>
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<tr>
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<td><code>org.dspace.app</code></td>
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<td>Application layer</td>
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</tr>
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<tr>
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<td><code>org.dspace</code></td>
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<td>Business logic layer
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(except <code>storage</code>
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and <code>app</code>)</td>
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</tr>
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<tr>
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<td><code>org.dspace.storage</code></td>
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<td>Storage layer</td>
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</tr>
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</tbody>
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</table>
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<p>The storage and business logic
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layer APIs are extensively documented
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with Javadoc-style comments. Generate the HTML version of these by
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entering the source directory and running:</p>
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<pre>ant public_api</pre>
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<p>The package-level documentation
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of each package usually contains an
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overview of the package and some example usage. This information is not
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repeated in this architecture document; this and the Javadoc APIs are
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intended to be used in parallel.</p>
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<p>Each layer is described in a
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separate section:</p>
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<ul>
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<li><a href="storage.html">Storage Layer</a>
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<ul>
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<li><a href="storage.html#rdbms">RDBMS</a></li>
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<li><a href="storage.html#bitstreams">Bitstream Store</a></li>
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</ul>
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</li>
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<li><a href="business.html">Business Logic Layer</a>
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<ul>
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<li><a href="business.html#core">Core Classes</a></li>
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<li><a href="business.html#content">Content Management API</a></li>
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<li><a href="business.html#workflow">Workflow System</a></li>
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<li><a href="business.html#administer">Administration Toolkit</a></li>
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<li><a href="business.html#eperson">E-person/Group Manager</a></li>
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<li><a href="business.html#authorize">Authorisation</a></li>
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<li><a href="business.html#handle">Handle Manager/Handle
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Plugin</a></li>
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<li><a href="business.html#search">Search</a></li>
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<li><a href="business.html#browse">Browse API</a></li>
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<li><a href="business.html#history">History Recorder</a></li>
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<li><a href="business.html#checker">Checksum Checker</a></li>
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</ul>
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</li>
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<li><a href="application.html">Application Layer</a>
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<ul>
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<li><a href="application.html#webui">Web User Interface</a></li>
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<li><a href="application.html#oai">OAI-PMH Data Provider</a></li>
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<li><a href="application.html#itemimporter">Item Importer
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and Exporter</a></li>
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<li><a href="application.html#transferitem">Transferring
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Items Between DSpace Instances</a></li>
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<li><a href="application.html#registration">Registration</a></li>
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<li><a href="application.html#mets">METS Tools</a></li>
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<li><a href="application.html#mediafilters">Media Filters</a></li>
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<li><a href="application.html#filiator">Sub-Community
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Management</a></li>
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</ul>
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</li>
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</ul>
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<hr>
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<address> Copyright ©
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2002-2004 MIT and Hewlett Packard </address>
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</body>
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</html>
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