Structured entity relationship model: Difference between revisions

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The '''SERM''' (Structured'''structured Entityentity Relationshiprelationship 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 19891988. 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.

* SERM is already in the [[third normal form]]

==References==

{{reflist}}

[[Category:Data modeling]]

[[Category:Diagrams]]

[[Category:Modeling languages]]

[[de:Structured-Entity-Relationship-Modell]]