I just started looking at foundation db and I have some trouble understanding how the layers work. Are foundationdb layers interoperable? If I add data using sql, can i then query that data using the graph layer? How does that conversion/mapping work? Regards Oskar
Short answer regarding the SQL layer: not yet.
Longer answer:
The FoundationDB storage engine maintains a mapping from bytes to bytes, with no additional encoding or structure imposed on top of that. This being the case, interoperability between layers is certainly possible, and in some cases may be a design goal.
A common set of encodings used by many layers is provided by the Tuple Layer (https://foundationdb.com/documentation/data-modeling.html#tuples), so higher-level layers using the Tuple Layer will, for instance, pack identical primitive values to identical strings of bytes. For true interoperability between two layers, however, each layer will have to understand the logic by which the other represents its higher-level data structures in terms of Tuples.
As for the SQL layer, interoperability with other data model layers released by FoundationDB is definitely a medium-term goal. But you can't automatically in the current Alpha version.