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<concept id="GUID-053FFF2B-6FB1-5065-B9D1-047477F3DE01" xml:lang="en"><title>Introduction
to dictionary stores</title><shortdesc>A dictionary store is a store where all streams are accessed through
a UID, rather than directly by stream ID.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>A dictionary store contains streams in the usual way but, in addition,
the root stream is a stream dictionary. That is, the external representation
of a <codeph>CStreamDictionary</codeph> object is a list of two-way associations
between UIDs and stream ids.</p>
<p>The following diagram illustrates the concept of the dictionary store.</p>
<fig id="GUID-6EEADFD0-FFCD-513F-BC26-99B46B54D600">
<title>Dictionary store</title>
<image href="GUID-22699952-D032-5B69-B38A-43347A40A420_d0e355499_href.png" placement="inline"/>
</fig>
<p>The interface to a dictionary store is provided by the <codeph>CDictionaryStore</codeph> abstract
class. The classes for concrete dictionary stores are derived from this abstract
class; for example, <codeph>CDictionaryFileStore</codeph> is a concrete dictionary
store class which is implemented using a file store. </p>
<p>Note that a dictionary store does not derive from <codeph>CStreamStore</codeph>,
but owns a persistent store, a <codeph>CPersistentStore</codeph> type, and
a stream dictionary, a <codeph>CStreamDictionary</codeph> type, as part of
its implementation.</p>
<p><b>See also</b> </p>
<p><xref href="GUID-5592E9C1-D490-538F-9B11-5EFB72DEDBE2.dita">File based dictionary
store</xref> </p>
<p><xref href="GUID-F535B464-3125-549B-9130-E59B64C4B865.dita">Stream dictionaries</xref> </p>
<p><xref href="GUID-A928E956-9800-5277-B0D3-34BBB2707AE1.dita">Stream ID</xref> </p>
<p><xref href="GUID-95DF676F-F9BA-56E0-A4DE-E68B42C06932.dita">UID manipulation</xref></p>
</conbody></concept>