The Document isn’t listed in the specification overview of the ECMA-376 specification in the Forward part to Part I "Fundamentals", and the status is unknown, as well as it’s purpose. The overall impressions is as that of an promotional whitepaper

Overview document change status to informative in an annex.

Office Open XML Overview

Ed

Proposed Disposition of DIS 29500 Comment DK-0043 (Modified: 2007-10-27) The document “Office Open XML Overview” was intended to provide some background and contextual information about OOXML for reviewers during both the Ecma adoption stage and the 5-month Ballot stage of the Fast-Track process. (Such a document is often referred to as a white paper.) As such, this document will not be included in the published standard. Similar Comments: CA-0002 , DE-0140 , GB-0004 , GB-0006 , GB-0007 , GB-0008 , GB-0009 , GB-0010 , GB-0011 , GB-0015 , IN- 0050 , JP-0018 , PT-0002 , US-0004