Documents created using the SEND RECORD command from previous versions of 4D can be imported into 4D v11 SQL using the RECEIVE RECORD command.
However, the opposite is not true. As of 4D v11 SQL, the internal format of documents created by the SEND RECORD command has changed. So any document created using SEND RECORD in 4D v11 SQL can not be imported into any previous versions of 4D.
Also, when using RECEIVE RECORD in 4D v11 SQL to import data from a previous version of 4D, if any records contain subtables, only the parent record will be imported.
For more information see manuals: "4D v11 SQL Upgrade" and "4D v11 SQL Conversion Guide", which can be downloaded from here:
4th Dimension Documentation