The '''SERM''' (Structuredstructured Entityentity Relationshiptelationship Modelmodel) is an amplification of the [[Entity-relationship model|ERM]] which is commonly used for [[data modeling]]. It was first proposed from Prof. Dr. [[Elmar Sinz|Elmar J. Sinz]] in 1988. The SERM is commonly used in the [[SAP AG|SAP]]-world for the [[data modeling]].<ref name="Röthlin2010">{{cite book|author=Michael Röthlin|title=Management of Data Quality in Enterprise Resource Planning Systems|url=https://books.google.com/books?id=wyheQllcyh0C&pg=PA118|year=2010|publisher=BoD – Books on Demand|isbn=978-3-89936-963-2|pages=118–}}</ref>
==Aims==
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# avoidance of unnecessary relationshiptypes
==SERM-Symbols symbols==
[[Image:SERM-Symbols.JPG|600px]]
==SERM-Example example==
[[Image:SERM-example.JPG]]
* [[Customer]] and article are independent entities
* Every order is referred to one customer. Orders without [[customer]]scustomers are illegal (order is an ER Typetype). [[Customer]]sCustomers 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 [[customer]]scustomers are illegal. [[Customer]]sCustomers 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.
