ooad1-5  Exercise 1: Reading the Bike Shop Diagram
=====================================================

shop.class.mmd (Mermaid):

  classDiagram
      direction LR
      class Customer
      class Bike
      class RepairJob {
          +invoice(pricing) int
      }
      class JobPart {
          quantity
      }
      class Part
      class Mechanic
      class Pricing {
          <<interface>>
          +price(job) int
      }
      class LabourPricing
      Customer "1" --> "0..*" Bike
      Bike "1" --> "0..*" RepairJob
      RepairJob "1" *-- "0..*" JobPart
      JobPart "*" --> "1" Part
      RepairJob "*" --> "1" Mechanic
      LabourPricing ..|> Pricing
      RepairJob ..> Pricing

ANSWERS
(a) Deleting a RepairJob deletes its JobParts: the filled diamond (composition) sits at RepairJob, so the job owns them. The Parts are not deleted: JobPart --> Part is a plain association, and a Part is stocked independently of any job.
(b) No. The arrow RepairJob --> Mechanic means a job can reach its mechanic; there is no arrow back, so a Mechanic does not hold a list of jobs. To list a mechanic's jobs you would search all jobs, or add a navigable link.
(c) No. In "Customer "1" --> "0..*" Bike" the multiplicity next to Customer is 1: every Bike has exactly one Customer. (Read the number at the end you are asking about: how many customers per bike.)
(d) "RepairJob ..> Pricing" (dotted, open arrow) is the dependency. RepairJob uses Pricing, here as a parameter of invoice(pricing), but keeps no field of that type.
(e) No: Pricing is marked <<interface>>, so it has no implementation. You can create LabourPricing, which realises it (dotted line, hollow triangle).

WHY THIS WORKS AS AN ANSWER
---------------------------
Each answer comes from one feature of the notation: the diamond for lifetime, the arrowhead for navigation, the multiplicity at the near end for "how many", the dotted open arrow for a brief use, and the stereotype for what can be instantiated. The diagram renders correctly; if you render it afterwards you will see the filled diamond on RepairJob's side of the line to JobPart and the dotted arrows described.