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<chapter xmlns:xi="http://www.w3.org/2001/XInclude"><title>Concepts</title>

<!-- Overview -->

<section><title>Overview</title>
<para>
The three concepts most fundamental to <command>rad</command> are
<emphasis>interfaces</emphasis>, objects that implement those
interfaces, and the namespace in which those objects can
be found and operated upon.  An interface defines
how a <command>rad</command> client can interact with an object.  An
object implements an interface, providing a concrete
behavior to be invoked when a client makes a request.  Lastly, the
namespace acts as <command>rad</command>'s gatekeeper, associating a
name with each object, dispatching requests to the proper object, and
providing meta-operations that let the client make queries about what
objects are available and what interfaces they implement.
</para>

<para>
Before discussing these three concepts any further, though, it is
important to understand a fourth: data and the typing system used by
<command>rad</command>.
</para>
</section>

    <!-- Section: Data -->

    <xi:include href="c-concepts-data.xml" />

    <!-- Section: APIs -->
<!-- Interfaces -->
<!-- - Methods -->
<!-- - Properties -->
<!-- - Events -->

    <xi:include href="c-concepts-apis.xml" />

    <!-- Section: Namespace -->
<!-- Namespace -->
<!-- - Names -->
<!-- - Objects -->
<!-- - Operations -->

    <xi:include href="c-concepts-namespace.xml" />

</chapter>