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Hi Guys im trying to draw a erd with uml notation according to a case study, but im having difficulties as im a beginner.

Case study:

1) A department have many employees, although each department must have at least three employees. Every employee works for one and only one department. every department has a manager - only one manager per department. Clearly a manager is an employee of the company, but not all employees are managers.

2) A department may have many machines and every machine is assigned to a specific department.

3) A machine may be reported for maintenance numerous times. maintenance is done on a machine only once on a given day. some machines are so new they many not have required any maintenance yet.

here is what i've drawn so far:


As i think that Zero or more machines can be reported for maintenance and that Zero or more machines are maintained then there is a m:m relationship so we have to resolve it by adding a link entity. but im a bit confused on how to chose the Noun to describe the relation. and to solve it properly.

Edited by latinunit.net because: n/a
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here is the actual case scenario, ive made some more mods to the design and added more entities:

A department may have many employees, although each department must have at least three employees. Every employee works for one and only one department. Every department has a manager – only one manager per department. Clearly a manager is an employee of the company, but not all employees are managers.

A department may have many machines and every machine is assigned to a specific department. A machine may be reported for maintenance numerous times. Maintenance is done on a machine only once on a given day. Some machines are so new they may not have required any maintenance yet.

Products are produced on machines. A product can be an assembly of several different components or a single piece. Every product/component goes through one or more machines for appropriate production processes. Likewise several products may go through a particular machine for some standard process.
version 1

version 2

UMLERD.jpg 107.38 KB UMLERD2.jpg 178.33 KB
Edited by latinunit.net because: n/a
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