Complex business process operations can be effectively visualized with Entity Relational ER modeling. ER modeling is proven to be the best way to design and model relational databases, this design choice is based of Dr.Peter Chan’s papers published in 1976. Before discussing the M:M ring problem in ER modeling, I will brief description the basics of ER modeling.
Nouns in an english sentence are usually the entities ex: Customers, Company, Teachers etc. The physical properties of these nouns are attributes for entities. ex height, weight, date, etc.
Entities can be related to each other, the relation is usually verbs/ adverbs ex: “based on”. “for”, “basis off”, “bought from”, “operator of”, “issued for”, “stored in”, “responsible for” etc
Simple ER example would be “Customers can place Orders ”, in this example, the relation is called 1:M, one customer can place more than one order (m for many). In some cases, like social and a person would be a 1:1 relation, one person can have 1 social
Modeling employment history in entities is a bit of a pickle. For instance, consider entities person, company and position. Person can work at a company holding a position or, we can say a company hired a person for a position, or a position is held by a person employed at a company. Visually this can be as shown below.
It becomes increasingly tricky to answer the following question for each person we want to track the position held, for what company and how long. This configuration leads to what is known as M:M ring. This issue can be resolved by adding three other small entities as shown below.
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