The Microsoft Office XML formats (not to be confused with Office Open XML) are XML-based document formats (or XML schema

XML schema

An XML schema is a description of a type of XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed by XML itself...

s) introduced in versions of Microsoft Office

Microsoft Office

Microsoft Office is a non-free commercial office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft in August 1, 1989. Initially a marketing term for a bundled set of applications, the first version of...

 prior to Office 2007. Microsoft Office XP introduced a new XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 format for storing Excel spreadsheets and Office 2003 added an XML-based format for Word documents.

These formats were succeeded by Office Open XML (ECMA-376) in Microsoft Office 2007

Microsoft Office 2007

Microsoft Office 2007 is a Windows version of the Microsoft Office System, Microsoft's productivity suite. Formerly known as Office 12 in the initial stages of its beta cycle, it was released to volume license customers on November 30, 2006 and made available to retail customers on January 30, 2007...

.

File formats

• Microsoft Office Word 2003 XML Format — WordProcessingML or WordML (.XML)
• Microsoft Office Excel 2002 and Excel 2003 XML Format — SpreadsheetML (.XML)
• Microsoft Office Visio 2003 XML Format — DataDiagramingML (.VDX, .VSX, .VTX)
• Microsoft Office InfoPath 2003 XML Format — XML FormTemplate (.XSN) (Compressed XML templates in a Cabinet
  Cabinet (file format)
  In computing, CAB is the Microsoft Windows native compressed archive format. It supports compression and digital signing, and is used in a variety of Microsoft installation engines: Setup API, Device Installer, AdvPack and Windows Installer.Though Cabinet was originally called Diamond, its .CAB...
  
   file)

Limitations and differences with Office Open XML

Besides differences in the schema, there are several other differences between the earlier Office XML schema formats and Office Open XML.

• Whereas the data in Office Open XML documents is stored in multiple parts and compressed in a ZIP
  ZIP (file format)
  Zip is a file format used for data compression and archiving. A zip file contains one or more files that have been compressed, to reduce file size, or stored as is...
  
   file conforming to the Open Packaging Convention
  Open Packaging Convention
  The Open Packaging Conventions is a container-file technology initially created by Microsoft to store a combination of XML and non-XML files that together form a single entity such as an Open XML Paper Specification document...
  
  , Microsoft Office XML formats are stored as plain single monolithic XML
  XML
  Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
  
   files (making them quite large, compared to OOXML and the Microsoft Office legacy binary formats). Also, embedded items like pictures are stored as binary encoded blocks within the XML
  XML
  Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
  
  . In case of Office Open XML, the header, footer, comments of a document etc. are all stored separately.
• XML Spreadsheet documents cannot store Visual Basic for Applications
  Visual Basic for Applications
  Visual Basic for Applications is an implementation of Microsoft's event-driven programming language Visual Basic 6 and its associated integrated development environment , which are built into most Microsoft Office applications...
  
   macros, auditing tracer arrows, chart and other graphic objects, custom views, drawing object layers, outlining, scenarios, shared workbook information and user-defined function categories. In contrast, the newer Office Open XML formats support full document fidelity.
• Poor backward compatibility with the version of Word/Excel prior to the one in which they were introduced. For example, Word 2002 cannot open Word 2003 XML files unless a third-party converter add-in is installed. Microsoft has released a Word 2003 XML Viewer which allows WordProcessingML files saved by Word 2003 to be viewed as HTML
  HTML
  HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
  
   from within Internet Explorer
  Internet Explorer
  Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
  
  . For Office Open XML, Microsoft provides converters for Office 2003, Office XP and Office 2000.
• Office Open XML formats are also defined for PowerPoint 2007
  Microsoft PowerPoint
  Microsoft PowerPoint, usually just called PowerPoint, is a non-free commercial presentation program developed by Microsoft. It is part of the Microsoft Office suite, and runs on Microsoft Windows and Apple's Mac OS X operating system...
  
  , equation editing (Office MathML), vector drawing, charts and text art (DrawingML).

Word XML Format example

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w:right="1800"
w:bottom="1440"
w:left="1800"
w:header="720"
w:footer="720"
w:gutter="0" />