The proposal of using Software Defined Networking (SDN) techniques for operating optical transport networks has received a lot of attention. This approach provides centralised planning and control of network resources while collecting status and telemetry from the network to provide feedback and help with planning the delivery of services and optimising the network. A key component of SDN is how the central planning and management components communicate with the network equipment. The current approaches depend on a data model for each device, protocol, or component that is being controlled. These data models are most often written in the YANG language and passed between controller and device using the NETCONF protocol. Over the last several years a number of different standards organisations and open source initiatives have developed distinct modelling approaches for use in optical transport networks. Although the objectives are always the same, the models differ in details and high-level architecture meaning that equipment vendors, network management system developers, and network operators have to make choices or be faced with a complex ecosystem. It would be helpful if the various models and approaches could be consolidated to reduce the options while retaining flexible, high function. This paper makes a comparative analysis of the different data models available with a view to helping decision-makers understand the choices available.