Ch03 the requirements_specification
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The document discusses developing well-formed engineering requirements. It outlines that by the end of the chapter, the reader should understand properties of engineering requirements like being abstract, verifiable, unambiguous and traceable. It also discusses developing a complete requirements specification by identifying requirements from customers, environment and technical standards. Advanced analysis methods like tradeoff analysis are examined to refine requirements.
Ch03 the requirements_specification
- 1. Revised by S.P. Chew (2009)
- 2. By the end of this chapter, you should: Understand the properties of an engineering requirement and know how to develop well-formed requirements that meet the properties. Be familiar with engineering requirements that are commonly specified in electrical and computer systems. Understand the properties of the complete requirements specification, as well as knowing the steps to develop one. Be able to conduct advanced requirements analysis to identify tradeoffs. 2
- 3. Raw (Marketing) Requirement Customer Customer Feedback Customer Representation Develop Technical Feedback System Requirements Constraints & Technical Standards Representation Technical Environment Community 3
- 4. Properties: 1) Abstract • Specify what system will do, but not how it will be implemented. 2) Verifiable • Should be a way to measure or demonstrate that the requirement is met in the final system realization 4
- 5. 3) Unambiguous ◦ Each requirement should have a single unambiguous meaning ◦ Stated with short complete sentences 4) Traceable ◦ Valid in marketing requirements. 5
- 6. Does the following requirement meet the four desirable properties? (abstract, verifiable, unambiguous, traceable) “The robot must have an average forward speed of 0.5 feet/sec, a top speed of at least one foot/sec, and the ability to accelerate from standstill to the average speed in under one second.” 6
- 7. IMPORTANT – Your requirements for your project must also be REALISTIC. => You need to demonstrate that the target you have selected is technically feasible. How are you going to do this? 7
- 8. Constraint = design decision imposed by the environment or a stakeholder that impacts or limits the design. Example contraint: The system must use a PIC18F52 microcontroller to implement processing functions. 8
- 9. A standard is established way of doing things that ensure interoperability. Question is, what standards are relevant to your project and how do you use them? Different levels of usage ◦ User ◦ Implementation ◦ Developer Types: safety, testing, reliability, communication, dat a, documentation, design, metastandards and etc… 9
- 10. Structured workshops and brainstorming Interviews and surveys Observation of processes and devices in use Benchmarking and market analysis Prototyping and simulation Research survey 10
- 11. Need to know what type of requirement to select for a given system. These are but EXAMPLES – you must determine the correct ones for your system! Hint: don’t just try to copy and paste them. 11
- 12. Performance The system should detect 90% of all human faces in an image. The amplifier will have a total harmonic distortion less than 1%. Reliability & Availability The system will have a reliability of 95% in five years. The system will be operational from 4AM to 10PM, 365 days a year. 12
- 13. Energy The system will operate for a minimum of three hours without needing Environmental The system should be able to operate in the temperature range of 0°C to 75°C. The system must be waterproof and operate while submersed in water. to be recharged. Many more examples in the book. 13
- 14. Steps to follow to develop the requirements specification: ◦ Identify requirements from the customer, environment and technical community ◦ Ensure the engineering requirements are well formed ◦ Organize the requirements. Similar requirements should be presented together and relationship btwn. Engineering and marketing requirements identified. ◦ Validate the requirements specification. 14
- 15. Normalized/Orthogonal ◦ Should no overlap or redundancy between engineering requirements. Complete Set ◦ Addresses all the needs of the end user and also those need required for system implementation. 15
- 16. Consistent ◦ Should not be self-contradictory Bounded ◦ Determining the min acceptable bound for target values Modifiable 16
- 17. Ask the customer if the requirements meet their needs. Usually done in teams. For each engineering requirement ◦ Traceable? ◦ Verifiable? ◦ Realistic & technical feasible? For the complete Requirements Specification ◦ Orthogonal? ◦ Complete? ◦ Consistent? 17
- 18. Marketing Requirements Engineering Requirements Justification 1, 2, 4 1. The total harmonic Based upon competitive distortion should be <0.1%. benchmarking and existing amplifier technology. Class A, B, and AB amplifiers are able to obtain this level of THD. 1–4 1. Should be able to sustain This power range provides more an output power that than adequate sound throughout averages 35 watts with a the automobile compartment. It is a peak value of 70 watts. sustainable output power for projected amplifier complexity. 2, 4 1. Should have an efficiency Achievable with several different ( ) >40 %. classes of power amplifiers. 3 1. Average installation time for Past trials using standard audio and the power and audio power jacks demonstrate that this is connections should not a reasonable installation time. exceed 5 minutes. 18
- 19. 1–4 1. The dimensions should Fits under a typical car seat. not exceed 6” x 8”x 3”. Prior models and estimates show that all components should fit within this package size. 1–4 1. Production cost should not This is based upon competitive exceed $100. market analysis and previous system designs. Marketing Requirements 1.The system should have excellent sound quality. 2.The system should have high output power. 3.The system should be easy to install. 4.The system should have low cost. 19
- 20. Examined more advanced methods that are used to analyze and refine requirements Addresses tradeoffs between engineering and marketing requirements, tradeoffs between engineering requirement themselves and benchmarking 20
- 21. Output Power , Efficiency Install Time Dimensions THD Cost - + + - - - 1) Sound Quality + ↑↑ ↓ ↓↓ ↓↓ 2) High Power + ↓ ↑↑ ↑ ↓↓ ↓ 3) Install Ease + ↓ ↑↑ ↑ ↓ 4) Cost - ↓↓ ↓ ↓ ↓ ↑↑ 21
- 22. Output Power , Efficiency Dimensions Install Time THD Cost - + + - - - THD - ↓ ↓ ↓ Output Power + ↑ ↓ ↓ , Efficiency + ↑ ↓ Install Time - ↓ Dimensions - ↓ Cost - 22
- 23. Apex Audio Monster Amps Our Design THD 0.05% 0.15% 0.1% Power 30W 50W 35W Efficiency 70% 30% 40% Cost $250 $120 $100 23
- 24. A complete requirements document will contain: Needs, Objectives, and Background (See Chapter 2). Requirements. ◦ marketing requirements ◦ engineering requirements Should be abstract, verifiable, and traceable Some maybe constraints Some may be standards ◦ Advanced analysis Engineering-marketing tradeoffs Engineering-engineering tradeoffs Benchmarks 24
- 25. Properties of engineering requirements Examples of engineering requirements Properties of the Requirements Specification Advanced Requirements Analysis ◦ Tradeoff matrices ◦ Benchmarks 25