Migration of legacy assets to SOA embodies a key software engineering challenge. Over a decade there has been an increasing interest in the approaches addressing SOA migration. These approaches mainly differ in `what is migrated' and `how the migration is performed'. Such differences aggravate achieving a general understanding of `what SOA migration entails'. We describe what such migration process entails and what distinct conceptual elements systematically define the process. Based on the comprising conceptual elements the framework which is considered as a basis for understanding and assessment of different approaches is proposed. Further, the role of the migration framework in positioning and assessing the existing methods, is discussed. Finally, the procedure for positioning and mapping of migration approaches on the framework is explained using two example migration processes
