When you first create a BOM for a material, the system automatically creates the first alternative. The technical type of the BOM is not yet defined, so the technical type is " " (blank). The following graphic shows the structure of a "simple" BOM.

Some companies produce many similar products that have a lot of common parts. To reduce the workload for creating BOMs, you can extend a simple BOM to create a composite BOM, known as a "BOM group".