Notifications can optionally have a type indicator. Although neither client or nor server must support this, some may choose to. Those servers implementing categories may use them to intelligently display the notification in a certain way, or group notifications of similar types.
Categories are in class.specific form. class specifies the generic type of notification, and specific specifies the more specific type of notification.
If a specific type of notification does not exist for your notification, but the generic kind does, a notification of type class is acceptable.
Third parties, when defining their own categories, should discuss the possibility of standardizing on the hint with other parties, preferably in a place such as the xdg mailing list at freedesktop.org. If it warrants a standard, it will be added to the table above. If no consensus is reached, the category should be in the form of "x-vendor.class.name."
The following table lists standard notifications as defined by this spec. More will be added in time.
Table 2. Categories
|"device"||A generic device-related notification that doesn't fit into any other category.|
|"device.added"||A device, such as a USB device, was added to the system.|
|"device.error"||A device had some kind of error.|
|"device.removed"||A device, such as a USB device, was removed from the system.|
|"email"||A generic e-mail-related notification that doesn't fit into any other category.|
|"email.arrived"||A new e-mail notification.|
|"email.bounced"||A notification stating that an e-mail has bounced.|
|"im"||A generic instant message-related notification that doesn't fit into any other category.|
|"im.error"||An instant message error notification.|
|"im.received"||A received instant message notification.|
|"network"||A generic network notification that doesn't fit into any other category.|
|"network.connected"||A network connection notification, such as successful sign-on to a network service. This should not be confused with device.added for new network devices.|
|"network.disconnected"||A network disconnected notification. This should not be confused with device.removed for disconnected network devices.|
|"network.error"||A network-related or connection-related error.|
|"presence"||A generic presence change notification that doesn't fit into any other category, such as going away or idle.|
|"presence.offline"||An offline presence change notification.|
|"presence.online"||An online presence change notification.|
|"transfer"||A generic file transfer or download notification that doesn't fit into any other category.|
|"transfer.complete"||A file transfer or download complete notification.|
|"transfer.error"||A file transfer or download error.|