A dependent relationship between files is defined in a description block. A "description block" indicates the relationship among various parts of the program. It contains commands to bring all components up to date. The description file can contain up to 1024 description blocks.
Description File Description Block ┌──────────────┐ ┌───────── ┌───────────────────────────┐ │ Description │ │ │ │ │ Block 1 │ │ │targets... : dependents... │ ├──────────────┤─────┘ │ command │ │ Descr Blk 2 │ │ command │ ├──────────────┤─────┐ │ command │ │ : │ │ │ : │ ├──────────────┤ │ │ │ │ Descr Blk n │ │ │ │ │ │ │ │ │ └──────────────┘ └───────── └───────────────────────────┘