1. A computer-implemented method of mapping data within a data source to a target data model comprising: determining an identifier for each data object of the data source based on the data within that data object, wherein the identifier indicates for that data object a corresponding entity within a representation of a data model of the data source; comparing the determined identifiers for the data objects of the data source to the target data model to determine mappings between the data objects of the data source and the target data model; and extracting data objects from the data source for the target data model in accordance with the mappings.