In LibreOffice 6.0.5.2, what is the difference between
i) Calc : “microsoft excel 2007-2013 xml (.xlsx)” AND “Open office xml spreadsheet (.xlsx)” formats?
ii) writer : “microsoft word 2007-2013 xml (.docx)” AND “Open office xml text (.docx)” formats?
iii) Impress : “microsoft powerpoint 2007-2013 xml (.pptx)” AND “Open office xml presentation (.pptx)” formats?
Do you mean office open xml instead of open office xml?
The good question would be to ask for differences between M$ Office and LibreOffice…
Files, and their formats, is only a means to encode primitives for storage and exchange. Although both suites try to export their abstract documents in a way defined by the Open Document Format, you cannot expect full compatibility between suites because they are based on different principles.
For instance, LO Writer is heavily based on styles. Consequently, it exports many dictionaries corresponding to paragraph, character, page, frame, list, … styles. M$ Word, on its side, only exports paragraph styles and a style sheet. This does not mean that M$ Word can’t format other elements such as words or pages., only it does it differently.
As a consequence, whenever a file is cross-read, the importing suite must translate the other’s encoding into its own primitives (dictionaries). It does not always succeed for various reasons. A feature may not exist or its design conflicts with the other. Also, the encoding may not be public: developers must guess how it is done and what’s its purpose in obscure cases.
Both suite use XML because XML is supposed to be self-descriptive. However, it is such a general format that, even if you have access or share the same DTDs, you can still have a diverging semantics.
Nevertheless, even if mutual understanding (compatibility) is not perfect, it is already a step towards easy document exchange.
You clearly mean Office Open XML, an ISO certified file format developed by Microsoft. Instead of using that open format (that just means the file structure definition is public so third party developers don’t have to reverse engineer it), MS saves files in a “transitional” version that deviates from the ISO standard in many ways, presumably to keep the competition at bay. That “transitional” version is the default “Microsoft Word 2007-2013 xml (.docx)” (for Word).