In abba the specific abbreviations are abstracted away from the program itself. So, while the New Abbreviations will be the main data set that I write for myself, it's important that any user be able to write whatever set of abbreviations they would like to see.
Right now the abbreviation definitions are stored in a json file that describes a series of sets of regular expression transforms. One exciting feature that I'm working on right now is my own markup language for describing abbreviations to make them easier to write.
Right now each abbreviation is stored as a regular expression that it matches to, its name, and then its realization in a given renderer (unicode is the one I'm starting with), if it has one. But I intend for the user to be able to use a much simpler patterning system if they like, for instance, writing er.terminal.initial which the system will compile into "er(?=\\b)|(?=\\b)er", and so on.