EDIT: This answer contains several inaccuracies. I (@oweng) have tried to edit it, but the site keeps dying, so I have posted a separate answer.
Sorry the answer to the ASKED question.
Why [does] Writer offer TWO option of saving document in DOCS format?
1. Microsoft 2007/2010 docx
2. Office Open XML docs
From wikipedia
1) Microsoft 2007/2010 docx
The Microsoft Office XML formats are XML-based document formats (or XML schemas) introduced in versions of Microsoft Office prior to Office 2007. Microsoft Office XP introduced a new XML format for storing Excel spreadsheets and Office 2003 added an XML-based format for Word documents.[1]
These formats were succeeded by Office Open XML (ECMA-376) in Microsoft Office 2007.
2) Open Office XML docs
Office Open XML (also informally known as OOXML or OpenXML) is a zipped, XML-based file format developed by Microsoft[2] for representing spreadsheets, charts, presentations and word processing documents. The Office Open XML specification was initially standardised by Ecma (as ECMA-376) and later by ISO and IEC (as ISO/IEC 29500).
Starting with Microsoft Office 2007, the Office Open XML file formats have become the default[3] target file format of Microsoft Office.[4][5]
Does it mean that 2nd option means FULL compliance
with ISO/IEC 29500:2008/ECMA-376 2nd edition (2008),
as MSO 2007/2010 is, as known, not fully compatible
with these standards?
Good question! @Khawar Nehal might have more info on this point. Per what he discovered on Wikipedia:
Microsoft Office 2010 provides read support for ECMA-376, read/write support for ISO/IEC 29500 Transitional, and read support for ISO/IEC 29500 Strict.[6] Microsoft Office 2013 additionally supports both reading and writing of ISO/IEC 29500 Strict.[7]
I'm not sure what that means for LO's support of this format.
Regards,
Khawar Nehal
http://dubai-computer-services.com
and
@qubit
I also would like to know the answer to this question. Microsoft Office 2013 is finally able to read and write the ISO/IEC 29500 strict (standardized Office Open XML) file format. MS Office 2010 was only able to read the strict format and MS Office 2007 could neither read nor write the strict format. Does the save option "Office Open XML" in LibreOffice refer to the strict standard?
I also would like to know the answer to this question. Microsoft Office 2013 is finally able to read and write the ISO/IEC 29500 strict (standardized Office Open XML) file format. MS Office 2010 was only able to read the strict format and MS Office 2007 could neither read nor write the strict format. The .docx, .xlsx and .pptx saved by Office 2007 and 2010 were only complying to the OOXML transitional standard.