Draw an E-R diagram to model the following situation. Be sure to include in your diagram all the relevant entities, attributes, relationships, functionality (N:1 or N:M) and whether any are mandatory. ER Diagram can be in MS Word.
[HINT: There are 3 entities and 2 relationships in the model answer].
A bus depot includes a maintenance section that repairs faulty buses. Each bus is identified by its fleet number, its make, the year it was manufactured and its registration number. When a vehicle breaks down, a report is submitted describing the nature of the problem and the time when the incident occurred. These reports are consecutively numbered as they are received and include the time when the bus was returned to the depot for repair. One or more mechanics fix the bus. Mechanics are identified by their staff number, name and qualifications. The time when each bus is ready for service after repair is recorded and also the time spent by each mechanic on each repair job.
Steps for constructing Entity-Relationship diagrams
1. Identify the entities and relationships in the English description.
2. For each entity draw and label a rectangle
3. For each relationship draw and label a diamond between the appropriate entities
4. Link the relationships to the entities using straight lines
5. List the attributes of each entity (and, if applicable, relationship)
6. Identify the key attribute for each entity
7. Label the links with the functionality of the relationship (1:1, 1:N or N:M)
8. Work out the membership class of each entity in each relationship (optional or mandatory)