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22 <div class="glossary">
23 <div class="titlepage"><div><div><h1 class="title">
24 <a name="glossary"></a>Glossary</h1></div></div></div>
27 <a name="action"></a><span class="glossterm">Action</span>
31 An <em class="firstterm">Action</em> is a method call on a
32 <em class="glossterm">Service</em>, which encapsulated a single piece of
33 functionality. Actions can have multiple input and output arguments, and
34 can return error codes. UPnP allows one of the output arguments to be
35 marked as the <em class="firstterm">return value</em>, but GUPnP doesn't treat
36 return values specially.
39 Every action argument has a related <em class="glossterm">State Variable</em>,
40 which determines the type of the argument. Note that even if the argument
41 wouldn't need a state variable it is still required, due to historical
46 <a name="controlpoint"></a><span class="glossterm">Control Point</span>
48 <dd class="glossdef"><p>
49 A <em class="firstterm">Control Point</em> is an entity on the network which
50 communicates with other <em class="glossterm">Devices</em> and
51 <em class="glossterm">Services</em>. In the client/server model the control
52 point is a client and the <em class="glossterm">Service</em> is a server,
53 although it is common for devices to also be a control point because
54 whilst a single control point/service connection is client/server, the
55 UPnP network as whole is peer-to-peer.
58 <a name="device"></a><span class="glossterm">Device</span>
62 A <em class="firstterm">Device</em> is an entity on the network which
63 communicates using the UPnP standards. This can be a dedicated physical
64 device such as a router or printer, or a PC which is running software
65 implementing the UPnP standards.
68 A Device can contain sub-devices, for example a combination
69 printer/scanner could appear as a general device with a printer
70 sub-device and a scanner sub-device.
73 Every device has zero or more <em class="glossterm">Services</em>. UPnP defines many standard
74 device types, which specify services which are required to be implemented.
75 Alternatively, a non-standard device type could be used. Examples of
76 standard device types are <code class="literal">MediaRenderer</code> or
77 <code class="literal">InternetGatewayDevice</code>.
79 <p>See Also <a class="glossseealso" href="glossary.html#service">Service</a>.</p>
81 <dt><span class="glossterm">DIDL-Lite</span></dt>
82 <dd><p>See <a class="glosssee" href="glossary.html#didllite">Digital Item Declaration Language - Lite</a>.</p></dd>
84 <a name="didllite"></a><span class="glossterm">Digital Item Declaration Language - Lite</span>
86 <dd class="glossdef"><p>
87 An XML schema used to represent digital content metadata. Defined by
90 <dt><span class="glossterm">SCPD</span></dt>
91 <dd><p>See <a class="glosssee" href="glossary.html#scpd">Service Control Protocol Document</a>.</p></dd>
93 <a name="service"></a><span class="glossterm">Service</span>
97 A <em class="firstterm">Service</em> is a collection of related methods
98 (called <em class="glossterm">Actions</em>) and public variables (called
99 <em class="glossterm">State Variables</em>) which together form a logical
103 UPnP defines standard services that define actions and variables which
104 must be present and their semantics. Examples of these are
105 <code class="literal">AVTransport</code> and <code class="literal">WANIPConnection</code>.
107 <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>
110 <a name="scpd"></a><span class="glossterm">Service Control Protocol Document</span>
112 <dd class="glossdef">
114 An XML document which defines the set of <em class="glossterm">Actions</em>
115 and <em class="glossterm">State Variables</em> that a
116 <em class="glossterm">Service</em> implements.
118 <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>
121 <a name="ssdp"></a><span class="glossterm">Simple Service Discovery Protocol</span>
123 <dd class="glossdef">
125 UPnP device discovery protocol. Specifies how <em class="glossterm">Devices</em>
126 advertise their <em class="glossterm">Services</em> in the network and also how
127 <em class="glossterm">Control Points</em> search for
128 services and devices respond.
130 <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>
132 <dt><span class="glossterm">SSDP</span></dt>
133 <dd><p>See <a class="glosssee" href="glossary.html#ssdp">Simple Service Discovery Protocol</a>.</p></dd>
135 <a name="state-variable"></a><span class="glossterm">State Variable</span>
137 <dd class="glossdef"><p>
138 A <em class="firstterm">State Variable</em> is a public variable exposing some
139 aspect of the service's state. State variables are typed and optionally
140 are <em class="firstterm">evented</em>, which means that any changes will be
141 notified. Control points are said to <em class="firstterm">subscribe</em> to
142 a state variable to receive change notifications.
144 <dt><span class="glossterm">UDN</span></dt>
145 <dd><p>See <a class="glosssee" href="glossary.html#udn">Unique Device Name</a>.</p></dd>
147 <a name="udn"></a><span class="glossterm">Unique Device Name</span>
149 <dd class="glossdef">
151 A a unique identifier which is <span class="emphasis"><em>unique</em></span> for every
152 device but <span class="emphasis"><em>never changes</em></span> for each particular
156 A common practise is to generate a unique UDN on first boot from a
157 random seed, or use some unique and persistent property such as the
158 device's MAC address to create the UDN.
160 <p>See Also <a class="glossseealso" href="glossary.html#device">Device</a>.</p>
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