We need to first discuss what kind of licenses are used in
the typical software service center. Based on our early work
in [7] [8] [9] and [10] as well as discussion with software
developers who work on data center management systems,
we identified five proprietary license types as the most common
ones in a data center out of fifteen basic licenses. The
five licenses are the time-based, the concurrent, the consumptive,
the cumulative, and the named license.