Solution : https://service.sap.com/sap/support/notes/66550 (SAP Service marketplace login required)
Key words : 
additional key words class node, prerequisites program error, class items, bom explosion, advance corrections, characteristics, restricted, components, specialization
Related Notes : 
       
| 162041 | Class node is not specialized automatically | 
| 51250 | 3.0F: Selection criteria for autom. specialization | 
| 51088 | 3.0F: Automatic specialization |