It should be obvious from the above ( and ) that a Channel's source and sink functions provide a flexible means of intercepting textual data that describes AST Objects as it flows in and out of your program. In fact, you might like to regard a Channel simply as a filter for converting AST Objects to and from a stream of text which is then handled by your source and sink functions, where the real I/O occurs.
This gives you the ability to store AST Objects in virtually any data system, so long as you can convert a stream of text into something that can be stored (it need no longer be text) and retrieve it again. There is generally no need to retain comments. Other possibilities, such as inter-process and network communication, could also be implemented via source and sink functions in basically the same way.
AST A Library for Handling World Coordinate Systems in Astronomy