This discription could be a literal or a resource. The answer to this is up to the application. Some application wants to handle version history. Other applications want to make sure the value doesn't change. But many applications probably wouldn't care and would like to just change the text value, without having to create a whole new object.
Literals are data.
Most of the time it's textual data. If it is a short piece of textual data, you would like to inline it in a xml representation. But if it's a large text, you will often prefere to refere to the text as an external objekt. If all literals would be modeld as a resource having a value property, we wouldn't have to make any diffrence between literals and other resources. The application could regard all literals as resources.