added comments as for review
added comments as for review


Former-commit-id: a5a93ef47be4450fc6483596f4a7a72f1df3bffc [formerly b8e4f3458e06ffb8c3045db2d7df4612a7ab385f]
Former-commit-id: c8e7e31e45f3c044f4e724bbdeead51159ced4a1
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine