Blu-ray has two modes of menu creation and navigation authoring - Movie Mode (HDMV) and BD-J (Java).
Movie Mode uses a virtual instruction set that is similar to computer assembly languages, ties in directly to the player status registers, and has 4,096 general purpose registers to hold information. (DVD is similar in concept, but has only 16 registers).
Movie mode controls its own private interactive 8-bit graphics layer (IG stream) which is laid on top of the primary and secondary video streams.