For every algorithm, it won't be perfect for all the problems. If the algorithm is designed for plugin, the algorithm will be re-used more easily. And maybe there will be a concept of algorithm server. The server will be required to perform some caculations and return the results. The caculation may be sessionless or may be session-related. Or the caculation will be smart to make some statistics analysis and to adjust itself for some similar problems.

Plugin may be an old things. But I think algorithm plugin, algorithm server, sessionless algorithm and session-related algortihtm is something new and interesting.