BOM is a computer file format used by the Mac OS X installer.
BOM stands for "bill of materials" and is used to determine which files to install, remove, or upgrade.
File information includes: the file's Unix file permissions, its owner and group, its size, its time of last modification, and so on.
Also included are a checksum of each file and information about hard links.
[1] Bill of materials (BOM) files are also used in printed circuit board (PCB) designing, where they contain a list of components to be put on the PCB.