opentraveldata/optd — pull request #30 by wolfer7 (2014-05-13 10:20:34+00:00)
Title: added from_date, to_date, env_id to ori_airline_alliance_membership.csv ...

...and updated alliance memberships.

This is a follow up to https://github.com/opentraveldata/optd/pull/22. From_date and to_date indicate when an airline joined / left the alliance. The env_id field indicates the version of the entry:
* An empty field marks the current version
* An integer value marks an older revision (starting from 1)