Level of abstraction for neural net operations

[anssiko]

(Related to the WebML WG Charter in development at #19)

WebNN explainer has a nice section that explains the rationale for the chosen level of abstraction for the neural network operations in WebNN API.

It was proposed we could integrate some of this explainer text into the next charter to provide more context on the level of abstraction. This could fit into the Scope section.

Tagging @wchao1115 @huningxin and @jbingham to confirm this would be appropriate.

[anssiko]

I'm proposing to add into the Scope section the following text adapted from the explainer:

For each high-level building block that decomposes into well-known lower-level operations, the APIs will informatively define a generic emulation path to allow for future extensibility.