Tags, use case 2: user vs. expert view

Consider an experiment where only a part of the devices should be visible to the general user but all devices should be available for an expert. Here is an excerpt from online.xml:

<?xml version="1.0"?>
<hw>
....
<device>
    <name>eh1a_mot01</name>
    <tags>expert,user</tags> 
    <type>stepping_motor</type>
    <module>oms58</module>
    <device>p20/motor/eh1a.01</device>
    <control>tango</control>
    <hostname>haspp20oh1:10000</hostname>
</device>
<device>
    <name>eh1a_mot02</name>
    <tags>expert</tags> 
    <type>stepping_motor</type>
    <module>oms58</module>
    <device>p20/motor/eh1a.02</device>
    <control>tango</control>
    <hostname>haspp20oh1:10000</hostname>
</device>
....
</hw>

All devices have an 'expert' tag. A subset of the devices is tagged with 'user'.

The following commands are possible:

online -tki -tags user
online -tki -tags expert
online -tki

Notice that in this case the '-tags expert' and the last command which has no tags parameter are equivalent.

Notice also that all devices have to be tagged with 'expert' because otherwise they would no be excluded by '-tags user'.