ISO/IEC specifies a set of conventions that are used by Office Open XML documents to define the structure and functionality of a package in terms of a package model . ISO/IEC was prepared by ISO/IEC JTC 1, Information technology, Subcommittee SC 34, Document description and processing languages. This third edition cancels and replaces the . This description focuses on the OPC format as specified in part 2 of ISO/IEC , Information technology -- Document description and processing languages -- Off