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<div class="section" id="identifier-management">
<h1>18.1. Identifier Management<a class="headerlink" href="#identifier-management" title="Permalink to this headline">¶</a></h1>
<dl class="docutils" id="index-0">
<dt>Author</dt>
<dd>Matthew B. Jones</dd>
<dt>Date</dt>
<dd><ul class="first last simple">
<li>20100301 [MBJ] Initial draft of Identifier documentation</li>
</ul>
</dd>
<dt>Goal</dt>
<dd>Extend Metacat to support identifiers with arbitrary syntax</dd>
<dt>Summary</dt>
<dd>Metacat currently supports identifier strings called ‘docids’ that have
the syntax ‘scope.object.revision’, such as ‘foo.34.1’ (we will refer to
these as ‘LocalIDs’). We now want Metacat to support identifiers that are
arbitrary strings, but still enforce uniqueness and proper revision
handling (refer to these as GUIDs). Metacat must be able to accept
these strings as identifiers for all CRUD operations, and reference them
in search results.</dd>
</dl>
<div class="section" id="identifier-resolution">
<h2>18.1.1. Identifier Resolution<a class="headerlink" href="#identifier-resolution" title="Permalink to this headline">¶</a></h2>
<p>Because Metacat uses LocalIDs throughout the code for references to objects,
and that LocalID has a constrained structure that includes semantics about
revisions in the identifier, it is difficult to wholesale replace it with
less-constrained string identifiers without re-writing much of Metacat.
Thus, our alternate strategy is to wrap the Metacat APIs with a
identifier resolution layer that keeps track of the unconstrained GUIDs and
maps them to constrained local identifiers which are used internally within
Metacat. The basic identifer table model is shown in Figure 1, while the
basic strategy for retrieving an object is shown in Figure 2, creating an
object is shown in Figure 3, updating an object in Figure 4, and deleting
an object is shown in Figure 5.</p>
<div class="section" id="identifier-table-structure">
<h3>18.1.1.1. Identifier Table Structure<a class="headerlink" href="#identifier-table-structure" title="Permalink to this headline">¶</a></h3>
<div class="figure" id="id1">
<img alt="_images/identifiers.png" src="_images/identifiers.png" />
<p class="caption"><span class="caption-text">Figure 1. Table structure for identifiers.</span></p>
</div>
</div>
<div class="section" id="handling-document-read-operations">
<h3>18.1.1.2. Handling document read operations<a class="headerlink" href="#handling-document-read-operations" title="Permalink to this headline">¶</a></h3>
<p>An overview of the process needed to read an object using a GUID.</p>
<div class="figure" id="id2">
<img alt="_images/guid_read.png" src="_images/guid_read.png" />
<p class="caption"><span class="caption-text">Figure 2. Basic handling for string identifiers (GUIDs) as mapped to
docids (LocalIDs) to retrieve an object.</span></p>
</div>
</div>
<div class="section" id="handling-document-create-operations">
<h3>18.1.1.3. Handling document create operations<a class="headerlink" href="#handling-document-create-operations" title="Permalink to this headline">¶</a></h3>
<p>An overview of the process needed to create an object using a GUID.</p>
<div class="figure" id="id3">
<img alt="_images/guid_insert.png" src="_images/guid_insert.png" />
<p class="caption"><span class="caption-text">Figure 3. Basic handling for string identifiers (GUIDs) as mapped to
docids (LocalIDs) to create an object.</span></p>
</div>
</div>
<div class="section" id="handling-document-update-operations">
<h3>18.1.1.4. Handling document update operations<a class="headerlink" href="#handling-document-update-operations" title="Permalink to this headline">¶</a></h3>
<p>An overview of the process needed to update an object using a GUID.</p>
<div class="figure" id="id4">
<img alt="_images/guid_update.png" src="_images/guid_update.png" />
<p class="caption"><span class="caption-text">Figure 4. Basic handling for string identifiers (GUIDs) as mapped to
docids (LocalIDs) to update an object.</span></p>
</div>
</div>
<div class="section" id="handling-document-delete-operations">
<h3>18.1.1.5. Handling document delete operations<a class="headerlink" href="#handling-document-delete-operations" title="Permalink to this headline">¶</a></h3>
<p>An overview of the process needed to delete an object using a GUID.</p>
<div class="figure" id="id5">
<img alt="_images/guid_delete.png" src="_images/guid_delete.png" />
<p class="caption"><span class="caption-text">Figure 5. Basic handling for string identifiers (GUIDs) as mapped to
docids (LocalIDs) to delete an object.</span></p>
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