* location (GPS coordinates and/or description)
* text/blob, possibly containing icon
* min/max trigger values
=== Sample session ===
;To HAL:
Here, it should be a good thing to have flags such as ''update_all_values'', ''used_cached_values''
<pre>
<command>
<describe />
</command>
</pre>
;From HAL:
<pre>
<hal name='HalName' target='event_main' backup_target='event_backup'>
<description>This device is a sample that does many things and actually nothing</description>
<location lat='47°00N' long='8°00E' elevation=495>Main door of building on route de Genève</location>
<devices>
<device
name='rfid_reader'
attrs='ro' type='rfid'
last_update_timestamp=1326310608
value='00EFC0B554' />
<device
name='door_lock'
attrs='rw'
type='enum'
value='closed'>
<value>open</value>
<value>closed</value>
<value>locked</value>
<value>unlocked</value>
</device>
<device
name='lock_delay'
attrs='rw'
type='int'
last_update_timestamp=1326310915
value=4
unit='s' />
<device
name='temperature'
attrs='ro'
type='float'
last_update_timestamp=1326312490
value=23.5
unit='°C'
alarm_high=28.0
warn_low=12.0/>
</devices>
</hal>
</pre>
;To HAL:
<pre>
<command>
<set device='door_lock' value='open' />
<get device='temperature' />
</command>
</pre>
;From HAL:
<pre>
<hal name='HalName'>
<devices>
<device name='door_lock' value='open' />
<device name='temperature' value=23.5 />
</devices>
</hal>
</pre>
== Hardware ==