This page lists a number of Air Transport Data Models.
They represent 'stripped-down' Models which contain the basics for a specific application area.
They are 'Canonical Models' that can be used as a common point of reference and a way of exchanging data between more detailed Models.
Here are some interesting comments on changes to the GDS Data Model, and options for a better GDS MOdel.

An interesting new player is Farelogix Platform
An interesting comment on deriving value from the CRS Data Model from NYU.
A good reference with a number of Data Models is ADRM.