A method for incrementally converting data items of a source repository that maintains a computer aided design, CAD, description according to a file based storage format to data items of an output repository that maintains the CAD description according to a relational database-based storage format, the method comprising: gathering, by a converter executing on an electronic device, data items of the source repository that maintains the CAD description according to the file based storage format; comparing, by the converter, current condition information for the gathered data items of the source repository with condition information as of a last successful conversion between the file based storage format and the relational database-based storage format in a synchronization information record maintained as a relational database separate from the source repository, the condition information of the synchronization information record including at least: identities of the data items of the source repository as of the last successful conversion, mappings of the data items of the source repository to corresponding data items of the output repository produced from conversion thereof, and state of the data items of the source repository as of the last successful conversion; in response to differences identified in the comparing, determining one or more new or changed data items in the source repository since the last successful conversion; converting, by the converter, the determined one or more new or changed data items to the relational database-based storage format of the output repository, while skipping any unchanged data items of the source repository, wherein the conversion creates or updates data items in the output repository; and updating the synchronization information record to include the current condition information for data items in the source repository. gathering, by a converter executing on an electronic device, data items of the source repository that maintains the CAD description according to the file based storage format; comparing, by the converter, current condition information for the gathered data items of the source repository with condition information as of a last successful conversion between the file based storage format and the relational database-based storage format in a synchronization information record maintained as a relational database separate from the source repository, the condition information of the synchronization information record including at least: identities of the data items of the source repository as of the last successful conversion, mappings of the data items of the source repository to corresponding data items of the output repository produced from conversion thereof, and state of the data items of the source repository as of the last successful conversion; in response to differences identified in the comparing, determining one or more new or changed data items in the source repository since the last successful conversion; converting, by the converter, the determined one or more new or changed data items to the relational database-based storage format of the output repository, while skipping any unchanged data items of the source repository, wherein the conversion creates or updates data items in the output repository; and updating the synchronization information record to include the current condition information for data items in the source repository. identities of the data items of the source repository as of the last successful conversion, mappings of the data items of the source repository to corresponding data items of the output repository produced from conversion thereof, and state of the data items of the source repository as of the last successful conversion; in response to differences identified in the comparing, determining one or more new or changed data items in the source repository since the last successful conversion; converting, by the converter, the determined one or more new or changed data items to the relational database-based storage format of the output repository, while skipping any unchanged data items of the source repository, wherein the conversion creates or updates data items in the output repository; and updating the synchronization information record to include the current condition information for data items in the source repository.