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24 <a name="glossary"></a>Glossary</h2></div></div></div>
27 <a name="action"></a>Action</dt>
30 An <em class="firstterm">Action</em> is a method call on a
31 <em class="glossterm">Service</em>, which encapsulated a single piece of
32 functionality. Actions can have multiple input and output arguments, and
33 can return error codes. UPnP allows one of the output arguments to be
34 marked as the <em class="firstterm">return value</em>, but GUPnP doesn't treat
35 return values specially.
38 Every action argument has a related <em class="glossterm">State Variable</em>,
39 which determines the type of the argument. Note that even if the argument
40 wouldn't need a state variable it is still required, due to historical
45 <a name="controlpoint"></a>Control Point</dt>
47 A <em class="firstterm">Control Point</em> is an entity on the network which
48 communicates with other <em class="glossterm">Devices</em> and
49 <em class="glossterm">Services</em>. In the client/server model the control
50 point is a client and the <em class="glossterm">Service</em> is a server,
51 although it is common for devices to also be a control point because
52 whilst a single control point/service connection is client/server, the
53 UPnP network as whole is peer-to-peer.
56 <a name="device"></a>Device</dt>
59 A <em class="firstterm">Device</em> is an entity on the network which
60 communicates using the UPnP standards. This can be a dedicated physical
61 device such as a router or printer, or a PC which is running software
62 implementing the UPnP standards.
65 A Device can contain sub-devices, for example a combination
66 printer/scanner could appear as a general device with a printer
67 sub-device and a scanner sub-device.
70 Every device has zero or more <em class="glossterm">Services</em>. UPnP defines many standard
71 device types, which specify services which are required to be implemented.
72 Alternatively, a non-standard device type could be used. Examples of
73 standard device types are <code class="literal">MediaRenderer</code> or
74 <code class="literal">InternetGatewayDevice</code>.
76 <p>See Also <a class="glossseealso" href="glossary.html#service">Service</a>.</p>
79 <dd><p>See <a class="glosssee" href="glossary.html#didllite">Digital Item Declaration Language - Lite</a>.</p></dd>
81 <a name="didllite"></a>Digital Item Declaration Language - Lite</dt>
83 An XML schema used to represent digital content metadata. Defined by
87 <dd><p>See <a class="glosssee" href="glossary.html#scpd">Service Control Protocol Document</a>.</p></dd>
89 <a name="service"></a>Service</dt>
92 A <em class="firstterm">Service</em> is a collection of related methods
93 (called <em class="glossterm">Actions</em>) and public variables (called
94 <em class="glossterm">State Variables</em>) which together form a logical
98 UPnP defines standard services that define actions and variables which
99 must be present and their semantics. Examples of these are
100 <code class="literal">AVTransport</code> and <code class="literal">WANIPConnection</code>.
102 <p>See Also <a class="glossseealso" href="glossary.html#action">Action</a>, <a class="glossseealso" href="glossary.html#device">Device</a>, <a class="glossseealso" href="glossary.html#state-variable">State Variable</a>.</p>
105 <a name="scpd"></a>Service Control Protocol Document</dt>
108 An XML document which defines the set of <em class="glossterm">Actions</em>
109 and <em class="glossterm">State Variables</em> that a
110 <em class="glossterm">Service</em> implements.
112 <p>See Also <a class="glossseealso" href="glossary.html#service">Service</a>, <a class="glossseealso" href="glossary.html#action">Action</a>, <a class="glossseealso" href="glossary.html#state-variable">State Variable</a>.</p>
115 <a name="ssdp"></a>Simple Service Discovery Protocol</dt>
118 UPnP device discovery protocol. Specifies how <em class="glossterm">Devices</em>
119 advertise their <em class="glossterm">Services</em> in the network and also how
120 <em class="glossterm">Control Points</em> search for
121 services and devices respond.
123 <p>See Also <a class="glossseealso" href="glossary.html#device">Device</a>, <a class="glossseealso" href="glossary.html#controlpoint">Control Point</a>, <a class="glossseealso" href="glossary.html#service">Service</a>.</p>
126 <dd><p>See <a class="glosssee" href="glossary.html#ssdp">Simple Service Discovery Protocol</a>.</p></dd>
128 <a name="state-variable"></a>State Variable</dt>
130 A <em class="firstterm">State Variable</em> is a public variable exposing some
131 aspect of the service's state. State variables are typed and optionally
132 are <em class="firstterm">evented</em>, which means that any changes will be
133 notified. Control points are said to <em class="firstterm">subscribe</em> to
134 a state variable to receive change notifications.
137 <dd><p>See <a class="glosssee" href="glossary.html#udn">Unique Device Name</a>.</p></dd>
139 <a name="udn"></a>Unique Device Name</dt>
142 A a unique identifier which is <span class="emphasis"><em>unique</em></span> for every
143 device but <span class="emphasis"><em>never changes</em></span> for each particular
147 A common practise is to generate a unique UDN on first boot from a
148 random seed, or use some unique and persistent property such as the
149 device's MAC address to create the UDN.
151 <p>See Also <a class="glossseealso" href="glossary.html#device">Device</a>.</p>
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