2 Custom UI
The subordinate clauses specify the semantics for the Custom UI XML markup contained within the ECMA-376 Office Open XML File Formats, as specified in [ECMA-376]. These semantics describe customization of the UI interface. Examples in the following clauses highlight customizations in the context of the Microsoft Office Fluent interface (UI) but the concepts extend naturally to any user interface.
Customization of the UI is accomplished via the addition of parts containing Custom UI XML markup to the containing document package.