1. Writing Product Requirements
translating customer words…
into
… realizable engineering requirements

2. Rationale for Requirements
Need to know the target and when you have reached it.
Agreement among stakeholders on product requirements before design begins.
Allows you to create a budget and schedule for product development.
Use requirements to prevent scope creep!

3. Needs  Requirements Technical specifications (measureable)
Customer Needs (subjective – what customer wants)
 Product Requirements
 System Requirements
 Component Requirements
Technical specifications (measureable)

4. Needs  Requirements Approach
Customer Needs (subjective – what customer wants)
Compile a list of needs
Organize by attributes (if possible)
Prioritize by importance
 Engineering Requirements
Define Metrics Specific
Benchmarking Measurable (units)
Set Target Values Achievable
Results-focused
Time-bound

5. Guidelines for Metrics
Each customer need  single metric (if possible)
Metrics  What the product must do (not how it will be achieved)
Consider criteria for comparison in marketplace (support the Value Proposition)

6. Needs-Metrics Matrix

7. Engineering Requirements
Be ready to show Engineering Requirements at Snapshot Day #1!!

8. Example
The noise from the motor shall be quiet enough for an operator to use it for a full 8 hour day. Requirement(s): Noise shall be no greater than 65 dBa in any operating condition as measured from the operator’s ear location. Operators: Range 5th %tile female to 95th %tile male

9. Appendix
Other info…

10. Process for Target Specs
Create a list of customer needs. (by-product of client interview)
Prioritize customer needs (by importance).
Prepare a needs-metrics matrix.
Compile benchmarking information.
Establish ideal as well as marginally acceptable values.
Set appropriate target values.

11. Tips on Selecting Metrics
Ideally each customer need would correspond to a single metric, and the value of that metric would correlate perfectly with meeting that need. In practice, several metrics may be necessary.
Metrics should be dependent, not independent, variables. Specs indicate what the product must do, but not how the specs will be achieved.
Show a table of metrics at first semester Snapshot event!

12. Tips on Selecting Target Values
5 ways to express target values… At least X
- At most X
- Between X and Y Exactly X
- A set of discrete values
Validate metrics and target values in your conceptual design review and again in your detail design review!

13. Summary
Requirements are typically established at least twice. Immediately after identifying the customer needs, the team sets target requirements.
After concept selection and testing, the team develops final requirements.
Final requirements are developed by thoroughly assessing actual techno-logical constraints and production costs. They should be based on rigorous analytical and physical modeling.

14. Process for Final Specs
Develop technical models of the product.
Develop a cost model of the product.
Refine target requirements, making well documented trade-offs as necessary.
Flow down requirements for overall system into sub-systems.
Set appropriate values for final requirements.

15. Helpful References
Ulrich and Eppinger, Product Design and Development, 5th Edition, McGraw Hill, Hatley and Pirbhai, Strategies for Real-Time System Specification, Dorset House, Rechtin and Maier, The Art of Systems Architecting, 2nd Edition, CRC Press, 2000.