Incremental mapping compilation in an object-to-relational mapping system
Philip A. Bernstein, Marie Jacob, Jorge Pérez, Guillem Rull, James F. Terwilliger · 2013
In an object-to-relational mapping system (ORM), mapping expressions explain how to expose relational data as objects and how to store objects in tables. If mappings are sufficiently expressive, then it is possible to define lossy mappings. If a user updates an object, stores it in the database based on a lossy mapping, and then retrieves the object from the database, the user might get a different result than the updated state of the object; that is, the mapping might not "roundtrip." To avoid this, the ORM should validate that user-defined mappings roundtrip the data. However, this problem is NP-hard, so mapping validation can be very slow for large or complex mappings.