+<a name="Dependencies.when.compiling"></a>
+<h2>Dependencies when compiling</h2>
+
+<p>Afb-daemon provides a configuration file for <em>pkg-config</em>.
+Typing the command</p>
+
+<pre><code>pkg-config --cflags afb-daemon
+</code></pre>
+
+<p>will print the flags to use for compiling, like this:</p>
+
+<pre><code>$ pkg-config --cflags afb-daemon
+-I/opt/local/include -I/usr/include/json-c
+</code></pre>
+
+<p>For linking, you should use</p>
+
+<pre><code>$ pkg-config --libs afb-daemon
+-ljson-c
+</code></pre>
+
+<p>As you see, afb-daemon automatically includes dependency to json-c.
+This is done through the <strong>Requires</strong> keyword of pkg-config
+because almost all plugin will use <strong>json-c</strong>.</p>
+
+<p>If this behaviour is a problem, let us know.</p>
+
+<p>Internally, afb-daemon uses <strong>libsystemd</strong> for its event loop
+and for its binding to D-Bus.
+Plugins developpers are encouraged to also use this library.
+But it is a matter of choice.
+Thus there is no dependency to <strong>libsystemd</strong>.</p>
+
+<blockquote><p>Afb-daemon provides no library for plugins.
+The functions that the plugin need to have are given
+to the plugin at runtime through pointer using read-only
+memory.</p></blockquote>
+
+<a name="Header.files.to.include"></a>
+<h2>Header files to include</h2>
+
+<p>The plugin <em>tictactoe</em> has the following lines for its includes:</p>
+
+<pre><code>#define _GNU_SOURCE
+#include <stdio.h>
+#include <string.h>
+#include <json-c/json.h>
+#include <afb/afb-plugin.h>
+</code></pre>
+
+<p>The header <em>afb/afb-plugin.h</em> includes all the features that a plugin
+needs except two foreign header that must be included by the plugin
+if it needs it:</p>
+
+<ul>
+<li><em>json-c/json.h</em>: this header must be include to handle json objects;</li>
+<li><em>systemd/sd-event.h</em>: this must be include to access the main loop;</li>
+<li><em>systemd/sd-bus.h</em>: this may be include to use dbus connections.</li>
+</ul>
+
+
+<p>The <em>tictactoe</em> plugin does not use systemd features so it is not included.</p>
+
+<p>When including <em>afb/afb-plugin.h</em>, the macro <strong>_GNU_SOURCE</strong> must be
+defined.</p>
+