No documentation on spec compliance

[rossturk]

There is not currently any documentation that explains which parts of the spec are optional and which are required.

For example, is it possible to have a dataset without any jobs? Or a job without any runs? Which facets, if any, are required for any given situation? Is provider required?

This could be very helpful for tool providers wishing to implement OpenLineage, but unsure whether their work (or intended work) counts as "implementing OpenLineage".

I recommend a page in the Core Specifications section that outlines the minimal requirements for someone to say that they "implement OpenLineage".