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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-983C5DB9-85EF-541E-B494-19E3E617914A" xml:lang="en"><title>Introduction

    13 to embedded stores </title><shortdesc>Data contained in a stream can represent a store in its own right

    14 rather than just objects. Such a store is known as an embedded store.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>The stream containing the embedded store is known as the host stream.</p>

    16 <p>It is often convenient, and sometimes necessary, to collect the streams

    17 representing a partial object network into an embedded store. This makes it

    18 easier for the streams representing such a partial object network to be deleted,

    19 by deleting (from the top level store) the stream containing the embedded

    20 store.</p>

    21 <p> The alternative is to traverse the individual streams representing the

    22 partial object network and deleting them in the correct sequence; this can

    23 be difficult.</p>

    24 <p>The following diagram shows the idea:</p>

    25 <fig id="GUID-612A6C2C-D706-50BB-A6C4-F2B5639685F8">

    26 <title>Embedded store within stream</title>

    27 <image href="GUID-8B1C7778-0C6D-5DEE-90FD-3B016EC0E3CE_d0e361437_href.png" placement="inline"/>

    28 </fig>

    29 <p>An embedded store can contain an arbitrarily complex network of streams.

    30 As well as being easy to delete, this stream network can also be copied by

    31 simply copying the host stream from the containing store.</p>

    32 <p>Embedded stores are persistent stores.</p>

    33 <p>The embedded store is constructed on a write stream in its containing store

    34 and, for writing, the embedded store behaves like a direct file store — once

    35 streams within the embedded store have been committed and closed, they cannot

    36 subsequently be changed, i.e. streams cannot be replaced, deleted, extended

    37 or changed in any way.</p>

    38 <p>Embedded stores are used for object embedding by the application architecture.

    39 Because the embedded store behaves like a direct file store, only document

    40 types with direct representations can be embedded. In particular, documents

    41 using permanent-type stores, such as the database or the agenda, cannot be

    42 embedded. Such documents may, however, contain any type of embeddable document.</p>

    43 <section id="GUID-72E3A832-7DE7-41F0-B021-BC37C6BB40DF"><title>See also</title> <p><xref href="GUID-C9D8D913-C65F-5A69-A606-30F59BFB38E2.dita">File stores</xref> </p> <p><xref href="GUID-B683496C-652E-5F48-924E-52D2FF3A78A7.dita">Direct file store</xref> </p> </section>

    44 </conbody></concept>