update test cases
[REFACTORING] rename class
[REFACTORING] rename class
[REFACTORING] rename class
[REFACTORING] rename data classes which are stored in database
[REFACTORING] rename data classes which are stored in database
[REFACTORING] move package
add an interface to represent data classes with volatile data
add templates of data classes with volatile information
implement Revision
implement Segment
implement CodeFragment