One desired attribute (of many) of the system is that is be “user friendly” What (if anything) will you do to achieve this?

Tom Gilb Competitive Engineering Butterworth-Heinemann, 2005 Famous for: EVO development model Software inspections Planguage and quantifications

Gilb’s Law: Anything you need to quantify can be measured in some way that is superior to not measuring it at all

Emphases from EVO Don’t forget non-functional requirements Quality attributes such as performance Resource attributes such as storage space Capacity attributes such as throughput Providing these can be more costly than the basic functionality Everything can and should be quantified Break it down into components Find the relevant scale for each one

Example: A Car Comfort Safety Speed Acceleration Capacity Seats Trunk space Fuel efficiency

Example: A Flower Fragrance Attractiveness colors Bloom frequency Pollen quantity Toxicity Watering requirements

Example: “Increased Ease of Service” Context: mobile phone specs This is a requirement from marketing What are the engineers supposed to do? How do we know that they did well?

Step 1: Find Components Serviceability has these components: Repair Enhancement Fashion changes Installation Reconfiguration …But these are just words

Step 2: Define and Agree on Gist Repair: speed of repair of faults under given conditions Enhancement: speed of introducing HW or SW Fashion changes: ease of customer changing accessories Installation: speed of installing in defined setting Reconfiguration: work-hours to modify for varied uses, e.g. coupling to PC or power supply

Step 3: Measurable and Testable For each identified component, define Scale (units) Practical way of measuring (meter) Apply to Benchmarks: current performance, state of the art, competitors Targets: this product, future products Constraints: what must be achieved

Example: Repair Definitions Ambition: substantially improve speed of repair under given conditions Scale: hours to repair or replace, from fault occurrence till fault-free use by customer where intended Meter: field test with at least 20 representative cases

Example: Repair Benchmarks Past [phone X, home market, qualified dealer shop]: 0.1 hours at shop hours for customer transit Record [competitor Y]: 0.5 hour average Trend [US market, large corporate users]: 0.3 hours

Example: Repair Targets / Constraints Goal [next release, urban areas, personal use]: 0.8 hours Goal [next release, US market, large coprporate users]: 0.2 hours <- marketing requirement Fail [next release, large coprporate users]: 0.5 hours on average Survival [next release, all markets]: 1.0 hours

Example: Ease of Access

Exercise Define a scale and meters for “user friendliness”