OpenXML

OpenXML refers to a set of XML-based file formats used to represent word processing, spreadsheet, and presentation documents. It underpins Office Open XML, the document formats introduced with Microsoft Office 2007 and later standardized by ECMA as ECMA-376 and by ISO/IEC as ISO/IEC 29500. The specifications define the structure and semantics of Word, Excel, and PowerPoint files and aim to enable interoperability and programmatic access.

OpenXML files are ZIP packages that follow the Open Packaging Conventions (OPC). A document consists of multiple XML parts and relationships, such as word/document.xml, word/styles.xml, and media and embedded objects, with relationships described in _rels/.rels and content types in [Content_Types].xml. The packaging model allows linking between parts and reuse of shared resources.

Common extensions include .docx, .xlsx, and .pptx for standard documents; .docm, .xlsm, and .pptm for macro-enabled variants. The formats support embedded data and media; macros are stored in separate parts and can raise security considerations for processing and execution.

Standardization and implementations: The Office Open XML formats were developed by Microsoft and standardized by ECMA and ISO/IEC. They are implemented by Microsoft Office and by other suites such as LibreOffice/OpenOffice, Apache POI, and the Open XML SDK. They are widely used for data interchange, archival, and automation. Real-world compatibility can vary across applications and versions, and feature support evolves with updates to the standards and implementations.