In object-oriented languages, dynamic object reclassification is a technique to change the class binding of an object at runtime. Current approaches express when and how to reclassify inside the programs, and focus on internal consistency (e.g., dynamic object reclassification must be type safe). These approaches are less suited for programs that need to be consistent with an external context, such as autonomous systems interacting with a knowledge base. This paper proposes declarative dynamic object reclassification, a novel technique that provides a separation of concerns between a program’s business code and its adaptation logic for reclassification, expressed via a knowledge base. We present Featherweight Semantically Reflected Java, a minimal calculus for declarative dynamic object reclassification that enables the programmer to define consistency both internally (using a type system) and externally (using declarative classification queries). We further implement the technique by extending SMOL, a language for reflective programming via external knowledge bases.