OMI import and export are enabled to handle BOM assemblies, which are hierarchically-structured BOM positions that can be created manually in the B.20.01 module or by copying Smart Reference Data assembly structures into the BOM by use of the BOM_COPY procedure in the B.20.01.41 module. OMI recognizes BOM assemblies by checking the value in the Assembly Level column (F-12).
An assembly must always have a main (or master) position. This position has assembly level 1. The next level in an assembly hierarchy is indicated by level 2; that is, a position with level 2 is created as a child position of the previous level 1 position. From each assembly POS record to the next in the import data, this level value may increase by 1, thus instructing OMI to open a new level. From each assembly POS record to the next, the level may decrease by any number; this instructs OMI to leave the previous level of the assembly hierarchy and return to the specified level for creation of a new (sub-) position. OMI maintains the state of its processing of BOM assembly structures in a stack data structure. If there are any inconsistent assembly records in the import data (for example, when a level increases by more than 1), an appropriate error message is written to the import protocol, and processing of the current assembly is cancelled; that is, it continues with the next valid POS or NODE_... record.
BOM assemblies can also have variable position attributes or document references on the sub-position level. For import, they are handled the same way as for main positions. For BOM data export on the B.20.01.44 screen, however, you have the option of specifying a method for attribute selection. The default on B.20.01.44 is to include only those attributes that are necessary for re-importing the exported data into a Smart Materials system with a similar setup of BOM attributes. Propagated attributes that have not been changed (as indicated by the Manual check box) on lower levels are not repeated in the export file for those lower levels of the node structure, or in the case of a BOM assembly, for lower levels of the assembly structure. This logic avoids attribute redundancy (these additional attribute records would be redundant because their value is already given by the implicit propagation logic in the BOM module).
As far as the structure itself is concerned, from a theoretical point of view, assembly structures could have an arbitrary depth; however, for practical reasons, this depth is limited to 14 levels.