DMN16 — Allow ONNX as well as PMML functions

ONNX https://onnx.ai/ is an open format for ML models that supports some model types, especially neural networks, better than PMML. DMN should consider allow ONNX functions as it does PMML functions.

Support ONNX as an alternative to PMML

ONNX is an alternative to PMML for interchanging ML and AI models. This proposal extends the Kind of functions to include the ONNX Kind. It uses a similar approach to the existing Java and PMML Kinds so that a function can be defined as the execution of an ONNX model.