This document appears to contradict itself when describing the minimum contents of a workbook.

In the "minimum workbook scenario" section, the minimum workbook is said to consist of:

A single sheet
A sheet ID
A relationship Id that points to the location of the sheet definition

However, in the "Generated SpreadsheetML" section, which is generated from code that purports to create such a minimal book, the diagram shows...

folder
workbook.xml
sheet.xml

If a workbook.xml is required, why is that not mentioned in the "minimum workbook scenario"? I believe the first part is referring to the object structure and the later to the files that represent that structure, but if this is the case it should really make that very clear.

Then a few lines later it says "The workbook.xml.rels file"... which is previously not mentioned. This file does not appear in the image of the minimal workbook. Is this file actually required? And am I correct in thinking the data earlier referred to as "A relationship Id" is stored in this .rels file?

Generally, I think it would make this document much easier to understand if the relationship between the concepts at the top and the actual files further down was clearly defined.