This is root element of whole qubes tree. Specifies minimal Qubes OS version. 3.0 Container for labels. Label which can be used by domain. One choice of colour for padlock icon. XML id attribute used for cross-referencing in properties' ``ref`` attribute. label-[0-9]+ Label's colour, HTML-like. #[0-9a-f]{6} [a-z0-9_-]+ Container for domains. One Qubes domain. Type of the domain. This specifies Python's class that is used for instantiation of this VM. XML id attribute used for cross-referencing in properties' ``ref`` attribute. domain-[0-9]+ Container for features. One feature of this domain. Name of the feature. [a-z0-9_-]+ [a-z0-9_-]+ Container for devices of particular class. Class of devices in this container. Currently the only supported is ``pci``. pci One device. This tag should contain some identifier, format of which depends on particular device class. [0-9a-f]{2}:[0-9a-f]{2}.[0-9a-f]{2} Container for user-defined tags. Tag value. Tags are not used anywhere by qubes core, they are for users reference. In the future they will be available for use in policies. Name of the tag. [a-z0-9_-]+ Container for properties. One property and its value specified either directly (as text contained in this tag) or as reference to another XML element in the tree (by ``ref=`` attribute). How it is saved, it depends on particular property. Property name. [a-z0-9_]+ Alternative property value, by reference to another XML element.