NetX offers a number of APIs, including REST, JSON/RPC, SOAP; and while there are others, these three are the primary interfaces for communicating with NetX.
The REST API is limited mainly to read-only calls in terms of accessing data. This is typically provided in XML format, but JSON is also available. However, because of the sheer expansiveness of NetX — and its vast number of methods — it is difficult to provide a truly "restful" web service; there are simply too many verbs to cover. This is why the "REST" API is mostly for reading data.
Additionally, it is important to point out that the REST API is the primary mechanism for retrieving files — asset originals, thumbnails and proxies, asset views and the like. In fact, the NetX HTML5 user interface relies solely on the REST API for file downloads. The exception to this is repurposing; if you want to transcode and retrieve the output, you will need to use either the SOAP, or JSON/RPC API.
The JSON/RPC is the newest API, and is recommended for any new development. It provide the broadest number of methods, and uses JSON as the format exchange. As mentioned above, this API is what the NetX HTML5 UI uses; so it is completely unabridged. Please refer to the JSON/RPC article for an introduction. The API is published here:
The SOAP API provides a near mirror to the JSON/RPC API — most of the method signatures are the identical; it's just the data communication format that is different. Technically speaking, the legacy NetX "Flex" user interface uses this API. Please refer to the SOAP article for more details.