Sustainability of Digital Formats: Planning for Library of Congress Collections

The Open XML Paper Specification (OpenXPS) is an open specification for a fixed, page-oriented, platform-independent document format and page description language. OpenXPS was approved by Ecma International as international standard ECMA-388 in June 2009. OpenXPS, using the .oxps extension, was based on Microsoft's proprietary XML Paper Specification (MS-XPS), which uses the .xps extension. However, Ecma International's Technical Committee 46 (TC46) introduced substantive changes. See Notes below for a list of the most important changes. Windows Vista and Windows 7 used XPS for printing to a file with the Microsoft XPS Document Writer, while Windows 8 and subsequent versions of Windows have used OpenXPS as the default format for that purpose. Open XPS has also been the basis for the Windows "XPS print path" since the release of Windows 8 in 2012. See Windows Presentation Foundation: Printing Overview and XPS Documents, aimed at developers of applications for Windows.

The OpenXPS specification was designed to support the tasks of distributing, archiving, rendering, and processing documents. The diagram on page 3 of Ecma OpenXPS White Paper (April 2009) from Ecma TC46 emphasizes that OpenXPS was not intended to support writing and editing. Among the high-level goals for the Open XPS specification listed in the white paper were that it should provide:

• A Page Description Language for communicating document content to and from document peripherals such as printers and scanners.
• A spool file format for processing and temporary caching within an operating system when interoperating with document peripherals such as scanners and printers.
• An electronic paper format for publication, sharing, storage and long term archiving of document content in a form that provides a facsimile of the physical paper representation.

According to the same OpenXPS white paper from TC46, the primary features that differentiated OpenXPS from other document formats (in 2009) were:

• Fixed layout representation of page content
• All resources must be included in the package
• XML-based mark-up used to define page content, file structure, and metadata
• Feature set limited to only that required for efficient electronic paper
• Minimal implementation requirements
• Minimal threat footprint for malicious code
• Supports fine-grained streaming and random access

The design objectives and the technical implementation of OpenXPS correspond closely to these of the proprietary predecessor from Microsoft. This format description will focus on the small but substantive differences. See MS-XPS for details on the structure and supported functionality of the OpenXPS variant.

Substantive differences between Microsoft's XPS format and OpenXPS: The differences listed below are in addition to many editorial changes, including re-organization to follow Ecma editorial practices and to allow removal of proprietary references, emphasizing that OpenXPS was designed for implementation independent of platform.

• Recommendations for identifying OpenXPS: To avoid confusion with the conventions used with XPS, OpenXPS recommends the use of .oxps as a filename extension and application/oxps as the content type. [Note: .xps and application/vnd.ms-xpsdocument have been used to identify XPS documents.]
• Namespace URI changes: the namespace URIs for the FixedPage markup and other parts of the specification were changed. In particular, http://schemas.openxps.org/oxps/v1.0 is the namespace URI for markup for the primary FixedDocumentSequence, FixedDocument, and FixedPage parts.
• Removal of references to Windows-specific features and schemas: The Microsoft Print Schema was dropped as a normative reference and as the only format for PrintTicket parts to convey user intent and device configuration settings to print systems. The requirement to support the Windows Color System (WCS) profile embedded as a private tag was removed.
• Improved color profile interoperability: OpenXPS producers and consumers are required to support color management using International Color Consortium (ICC) profiles conforming to the requirements of the ICC Color Profile specification, ICC.1:2001-04. Optionally, ICC profiles complying to ISO 15076-1:2005 (equivalent to the later ICC specification, ICC.1:2004-10) can also be included.
• Support for embedding raster images in JPEG XR format: Rather than permitting raster images in the Windows Media Photo (WMP) format to be embedded, OpenXPS supports embedding of JPEG XR, the successor of WMP adopted as a standard by ITU (International Telecommunication Union) in March 2009 and by ISO/IEC in August 2009. Through 2016, several new editions were published with minor corrections and changes that would not have affected the use of JPEG XR in OpenXPS. The 4th edition (from 2019) of the JPEG XR specification adds support for additional color encodings. The compilers of this resource assume that the new color encodings are not supported in OpenXPS files or implementations. Comments welcome.
• Support for new version of font format specification: The version of font format used by the OpenXPS format is ISO/IEC 14496-22:2007. Information technology — Coding of audio-visual objects — Part 22: Open Font Format.
• Support for embedding 3D models in X3D format: OpenXPS added support for the X3D standard to represent 3D content within the document. This support is implemented using the Markup Compatibility and Extensibility Specification standardized as Part 5 of ECMA-376 (OOXML) to ensure that there were no additional implementation requirements on existing applications that had already implemented support for XPS.

  The OpenXPS specification states that it allows incorporation of a 3D model in the X3D format, compliant with Interoperability conformance level as specified in ISO/IEC 19775-1:2008 (Architecture and base components), ISO/IEC 19776-1:2005 (XML encoding), or ISO/IEC 19776-3:2007 (Compressed binary encoding). [Note: ISO/IEC 19775-1:2013 does not mention an "interoperability" conformance level, but does specify an "Interchange Profile." Comments welcome.

  OpenXPS files that include 3D content must include a 'fallback" 2D alternative. The compilers of this resource have not located any examples of OpenXPS files that include 3D content. Nor have they explored whether particular viewers support display of 3D content. Comments welcome.

  Autodesk, developer of AutoCAD and other design products that incorporate 3D modeling functions, was represented in the TC46 working group that developed the OpenXPS specification. However, it is not apparent that Autodesk has used OpenXPS. One of the AutoCAD export formats is DWFx, which is described as based on the XML Paper Specification but not openly documented by Autodesk. All the DWFx files examined by the compilers of this resource used the XML namespaces associated with Microsoft's XPS format rather than those for OpenXPS. Some of these included resources that appeared to be in a 3D stream format that originated with HOOPS and is also found in DWF files; within the first few characters of the 3D part in the were "HSF V12.15" and "W3D". The compilers of this resource have found no evidence of use of OpenXPS with embedded 3D resources. Comments welcome.

Starting with Windows 8, the Microsoft XPS Document Writer available as a virtual printer has, by default, created an OpenXPS file, with extension .oxps.

As for the predecessor XPS format from Microsoft, there was little adoption other than in Windows. See MS-XPS.

A number of tools have been developed for viewing and converting XPS documents. See Useful References below.

Support for OpenXPS and XPS was dropped in 2018 in some applications or operating systems where they were supported previously. Features and functionality removed in Windows 10 indicates that starting with the April 2018 release, the XPS Viewer utility would require special action for installation in Windows. Adobe's Acrobat Pro (for Windows) used to import XPS files, but has withdrawn default support. Unable to convert XPS files to PDFs states, "With December 2018 release of Acrobat, converting XPS files to PDFs is disabled." Support can be re-enabled using the Windows Registry Editor.

As of early 2020, the virtual printer, Microsoft XPS Document Writer, continues to be available in Windows and to generate files in the OpenXPS format. Also, OpenXPS continues to be the basis for the newer of two primary Windows print paths. See Windows Print Path Overview. Also, see Printing experience in Google Chrome is expected to improve as Google embraces Microsoft’s XPS Print API for printing on Windows 10 for a November 2019 article indicating that Google Chrome was moving to use the newer print path based on OpenXPS.

No concerns. The Ecma International patent policy at the time OpenXPS was standardized was summarized as "The General Assembly of Ecma shall not approve recommendations of Standards which are covered by patents when such patents will not be licensed by their owners on a reasonable and non-discriminatory basis." Implementation of the OpenXPS specification is royalty-free because Microsoft's intent in submitting its XPS technology for standardization was to encourage wide use and interoperability.

Prior to submitting the XPS specification to Ecma International for standardization, Microsoft offered a royalty-free copyright license to copy and distribute the specification and a royalty-free patent license to implement and use XPS technology. See XML Paper Specification Licensing Overview (from 2006) and XML Paper Specification Licensing Overview (as online in early 2020).

The OpenXPS specification allows incorporation of a 3D model in the X3D format, requiring a 'fallback" 2D alternative for printing. See Description above.

The OpenXPS format (like its predecessor XPS format published by Microsoft) is not designed to support wordprocessing or document design. See MS-XPS.

See MS-XPS.

In place of Microsoft's own specification of the OpenType Font Format from 2004, the OpenXPS specification (ECMA-388) incorporates the successor format adopted as an international standard, published as ISO/IEC 14496-22: 2007: Information technology — Coding of audio-visual objects — Part 22: Open Font Format. ECMA-388 states, "The Open Font Format is considered to be equivalent to the OpenType font format." The 2007 version of the Open Font Format is downloadable from the ISO/IEC Information Technology Task Force (ITTF).

Version of OPC on which OpenXPS is based: See MS-XPS.

Formats allowed for embedded resources: The raster image formats that can be embedded in an OpenXPS document were selected for their wide support: JPEG in JFIF or EXIF containers; PNG; TIFF (compressed and uncompressed); and JPEG XR (formerly known as HD Photo and Windows Media Photo, see WMP).

Fonts are stored in font parts. OpenXPS permits the use of font formats as defined in ISO/IEC 14496-22:2007 (Information technology — Coding of audio-visual objects — Part 22: Open Font Format), including TrueType and CFF fonts. To support portability, the use of Unicode fonts is recommended in the specification. Fonts may be subsetted based on usage in the document. Although a subsetted font does not contain all the glyphs in the original font, it must be a valid Open Font Format file according to ISO/IEC 14496-22:2007. Fonts that may not be legally embedded may be obfuscated as a means of preventing casual misappropriation of embedded fonts. The specification specifies a method for obfuscation and recommends that the extension of an obfuscated Font part name be “.odttf” for TrueType fonts and “.odttc” for TrueType collections.