(Structured Entity Relationship Model) is an amplification of the ERM
which is commonly used for data modeling
. It was first proposed from Prof. Dr. Sinz in 1989. The SERM is commonly used in the SAP
-world for the data modeling
- structuring of large schemes
- visualization of existence dependency
- avoidance of inconsistencies
- avoidance of unnecessary relationshiptypes
- Customer and article are independent entities
- Every order is referred to one customer. Orders without customers are illegal (order is an ER Type). Customers without any orders are legal because they are independent Entities.
- To every order there is belonging at least one order item.
- Every order item is related to exactly one order.
- Every invoice is referred to one customer, as well. Invoices without customers are illegal. Customers without any invoice are legal.
- To every invoice there is belonging at least one invoice line item.
- Every invoice line item is related to exactly order item. An order item could be calculated or not.
- SERM is already in the third normal form