Can another committer please review https://github.com/apache/arrow/pull/34
This corrects a format specification inconsistency viz-a-viz the bitmap encoding null/not-null from the initial draft format documents. Note that this is orthogonal to the discussion about whether the concept of "non-nullable" (or "required") is a part of the physical memory layout or the schema metadata. I will propose a patch for ARROW-76 after this one is addressed. Thank you, Wes