OpenXPS or XPS stands for XML Paper Specification. It is based on XML and it's
 a new electronic paper format originally developed by Microsoft and it serves
 as a PDF alternative. XPS files are usually created using "Microsoft XPS
 Document Writer" in Windows environments. It is now standardized as an open
 standard document format.
 .
 Quoting Wikipedia:
 An XPS file is in fact a Unicoded ZIP archive using the Open Packaging
 Conventions, containing the files which make up the document. These include an
 XML markup file for each page, text, embedded fonts, raster images, 2D vector
 graphics, as well as the digital rights management information. The contents
 of an XPS file can be examined simply by opening it in an application which
 supports ZIP files.
 .
 The OpenXPS document format specification supports features such as color
 gradients, transparencies, CMYK color spaces, printer calibration,
 multiple-ink systems and print schemas.
 .
 This package contains the development files.