2.1.6 Future Record
The future record architecture enables an application that does not support certain records (section 2.1.4) to open and save the file while ignoring but preserving those records in the file. Records that contain an FRTHeader (section 2.5.135), FrtHeaderOld (section 2.5.136), FrtRefHeader (section 2.5.137), FrtRefHeaderNoGrbit (section 2.5.138). or FrtRefHeaderU (section 2.5.139) structure, as specified in this document, are future records and can be treated as such by an application that implements the future record architecture. Future records that are not supported by an application can be cached on load and persisted on save, enabling the data to be retained in the file for an application that does support those records. When loading and caching these unsupported records, an application can process range references associated with the unsupported records as specified in the FRTHeader, FrtHeaderOld, FrtRefHeader, FrtRefHeaderNoGrbit, or FrtRefHeaderU structures. The application can adjust these range references as cells are inserted, deleted or moved in the sheets (1) to preserve the correctness and validity of these range references associated with the unsupported records when saving the workbook along with the unsupported records.
For an in-depth discussion of how these structures relate to each other, read the specification for each structure in section 2.5.