The two processes communicate through a file-based protocol. The converter serializes [instructions](src/main/java/nu/marginalia/converting/instruction/Instruction.java)
to file, which are deserialized by the loader and fed into an [instructions](src/main/java/nu/marginalia/converting/instruction/Interpreter.java).
The instructions implement a visitor pattern.
Conceptually the pattern can be thought of a bit like remote function calls over file,
or a crude instructions-based programming language.