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Model a Weighting Scale (White Box level)

Now is the time to take the plunge and to exercice yourself with the following not guided wording.

DURATION​

You should be able to complete this exercise in 2 hours.

GOAL​

The objective is to go down a level of precision in the model, in order to have the same behavior as the BB level but showing the interactions between the functions that compose the WB.

You can reuse your model or start with our solution from the previous exercise.

MODEL VALIDATION BY SCENARIOS​

Your WB model must have the same behavior as the BB level, so the same scenarios will be reused to do the validation.

To remind you:

  1. Nominal Case:

    • The technician imports a price list,
    • The customer put products on the scale,
    • Once the scale is stabilized, the customer selects a kind of product,
    • After checking the kind of product and final price, the customer confirms to print a ticket.

  2. Degraded Cases:

    • The customer changes the weight at any operation of the process (during stabilization, after or before selecting a kind of product),
    • The customer cancels the ticket printing,
    • The Weighting Scale prints the last ticket.
    • The technician reloads tickets

BEFORE STARTING MODELLING​

  1. Identify your Functions
    Tips: you can split your service according to large families: HMI, sensors, calculators, etc.
  2. Define the states you will encounter in your State Machines (you should refine corresponding states as BB level)

If you have difficulty identifying functions, you can use the following decomposition.

FUNCTIONAL DECOMPOSITION​

The WB model decomposes into 5 essential functions:

  • Receive the weight: this function is used to acquire the weight and ensure its stability.
  • Calculate the price: responsible for calculating the price.
  • Print the ticket: used to print/cancel ticket printing.
  • Manage the number of tickets: update tickets number.
  • Process Price List: initialization of the file (you can use the provided CSV file) containing the product prices.

On the next page, you will find a solution we realized.