ECMA-376 defines a set of XML vocabularies for representing word-processing documents@ spreadsheets and presentations. On the one hand@ the goal of ECMA-376 is to represent faithfully the existing corpus of wordprocessing documents@ spreadsheets and presentations that have been produced by Microsoft Office applications (from Microsoft Office 97 to Microsoft Office 2008@ inclusive). It also specifies requirements for Office Open XML consumers and producers. On the other hand@ the goal is to facilitate extensibility and interoperability by enabling implementations by multiple vendors and on multiple platforms. This Part of ECMA-376 defines features for backward-compatibility and that are useful for high-quality migration of existing binary documents to ECMA-376. These features are used only by documents of conformance class WML Transitional (??1)@ SML Transitional (??1)@ or PML Transitional (??1). These features are sometimes needed for high-quality migration of existing binary documents to ECMA-376.