This article describes the technical specifications of the OpenDocument office document standard, as developed by the OASIS industry consortium. A variety of organizations developed the standard publicly and make it publicly accessible, meaning it can be implemented by anyone without restriction. The OpenDocument format aims to provide an open alternative to proprietary document formats. Document representation The OpenDocument format supports the following two ways of document representation: As a collection of several sub-documents within a package, each of which stores part of the complete document. This is the common representation of OpenDocument documents. It uses filename extensions such as .odt, .ott, .ods, .odp ... etc. The package is a standard ZIP file with different filename extensions and with a defined structure of sub-documents. Each sub-document within a package has a different document root and stores a particular aspect of the XML document. All types of documents (e.g. text and spreadsheet documents) use the same set of document and sub-document definitions. As a single XML document – also known as Flat XML or Uncompressed XML Files. Single OpenDocument XML files are not widely used, they are also unsupported on some office software which claims to support ODF (Microsoft Office applications version 2007 to 2013 do not recognize them). Filename extensions for a single OpenDocument XML documents are not defined in the OpenDocument technical specification, but commonly used are .xml, .fodt, .fods, ... etc. The recommended filename extensions and MIME types are included in the official standard (OASIS, May 1, 2005 and its later revisions or versions). The MIME types and extensions contained in the ODF specification are applicable only to office documents that are contained in a package. Office documents that conform to the OpenDocument specification but are not contained in a package should use the MIME type text/xml. The MIME type is also used in the office:mimetype attribute. It is very important to use this attribute in flat XML files/single XML documents, where this is the only way the type of the document can be detected (in a package, the MIME type is also present in a separate file mimetype). Its values are the MIME types that are used for the packaged variant of office documents. Documents The most common file extensions used for OpenDocument documents are .odt for text documents, .ods for spreadsheets, .odp for presentation programs, and .odg for graphics. These are easily remembered by considering ".od" as