Arnold Scene Source (.ass) is the native scene definition format, stored in human-readable, editable ASCII files.
MAXtoA lets you save scenes to .ass files that can later be rendered outside of 3ds Max with kick (a multi-platform, command-line utility) or used for rendering via Procedural.
'Export to Ass File' in the System tab of Render Setup
Exported .ASS files done in this way is more suitable for rendering with kick or on a render farm.
Kick.exe can be found in the C:\ProgramData\Autodesk\ApplicationPlugins\MAXtoA
However, in order to run it without errors from the command-line you may need to copy kick.exe, ai.dll and MAXtoA_Shaders.dll (plus any 3rd party shaders you may use) to another directory, otherwise the special adapter shader MAXtoA_Adapter.dll - which can not be run outside of 3ds max itself - will cause error messages.
You can also export to .ASS from the file menu. Choose File -> Export -> Export... and pick "Arnold Scene Source (.ASS)" from the file type menu, which also allows you to only export selected objects.
The files exported in this way is more suitable for use in procedural objects, since no render options are exported, and by default, only geometry and shaders are.