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The System in So Many Words

This article will show you how to talk to a client so that you are both on the same page when designing a system and understanding what it will be required to do. It is excerpted from Prefactoring,  Written by Ken Pugh (O'Reilly; ISBN: 596008740). Copyright 2007 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.

  1. The System in So Many Words
  2. Sam's Use Cases
  3. The Ilities
  4. What's in a Name?
  5. Splitters Versus Lumpers
By: O'Reilly Media
Rating: starstarstarstarstar / 2
May 15, 2008

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WE MEET SAM, THE CLIENT, FOR WHOM WE ARE DEVELOPING A SYSTEM. Tim, a co-developer, and I interact with Sam to get an overall view of what he wants the system to do through use cases and prototypes. We work together to determine a common vocabulary to describe the system's requirements.

Meet Sam

Systems are not developed in a vacuum. They are created to meet an organization's needs. The client for whom a system is developed is the source of the requirements for the system and is the final decider of whether a system meets those requirements. Sam, the client, represents a composite of clients for whom I have developed systems over the years.

Sam owns the business CD Rental and Lawn Mower Repair. He started out with lawn mower repair and discovered that people who use lawn mowers like to listen to CDs and they prefer listening to a different CD each time they mow. Therefore, Sam came up with the idea of renting CDs. The service started out as a whim, but it has grown dramatically.

Sam contacted me about creating a system for keeping track of rentals in his store. His current system of using cards similar to library cards works, but it is unable to provide him the reports he feels his growing business requires.

Currently Sam has only one store. Since business is booming, he is considering opening several more stores. He wants us to design the system not only so it works in his store today, but so he can change it easily to accommodate multiple stores tomorrow.

Tim the Developer

Tim introduced me to Sam. Tim studied computer science in college and worked summers at Sam's CD Rental and Lawn Mower Repair. He has been working as a programmer for five years, the last couple of years with me. He is back in school getting a master's degree. We still work together, but mostly remotely. He takes courses and does some teaching, so he is often unavailable during the day, when I am talking with Sam.

Tim represents an amalgamation of programmers with whom I have worked. We work together on approaches to solutions, but usually work separately on code due to the remoteness factor. Because of our physical separation, code readability is extremely important.

Sam's Request

Sam came up with some features that he wants to incorporate into his system. They are based on what he already does with his index cards, as well as additional ideas that he developed in his head. He listed them on a sheet of paper:

  1. I want to be able to keep track of where each CD is, both when it is in the store and when someone has rented it (including who has rented it).
  2. I want the system to report when CDs are overdue.
  3. I want a catalog so that customers can see what CDs are available and what songs are on them.
  4. When I have multiple stores, the system should show which stores have a particular CD.
  5. I want to be able to offer discounts to frequent renters.
  6. I want a charge system that enables me to bill customers per month rather than per rental.

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