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Software Engineering A PRACTITIONER’S APPROACH phần 7

t và thực hiện kiên cố để không. Ba nguyên tắc quan trọng hướng dẫn thiết kế giao diện người sử dụng có hiệu quả: (1) nơi người sử dụng trong kiểm soát, (2) giảm tải bộ nhớ của người sử dụng, và (3) làm cho giao diện nhất quán. Để đạt được một giao diện mà tuân thủ theo các nguyên tắc, | CHAPTER 19 TECHNICAL METRICS FOR SOFTWARE KEY CONCEPTS analysis metrics 517 architectural metrics.523 component-level metrics.526 design metrics . . 523 maintenance metrics.533 measurement principles.515 metrics attributes.516 quality factors. . 509 specification metrics.522 source code metrics.531 testing metrics. . 532 A key element of any engineering process is measurement. We use measures to better understand the attributes of the models that we create and to assess the quality of the engineered products or systems that we build. But unlike other engineering disciplines software engineering is not grounded in the basic quantitative laws of physics. Absolute measures such as voltage mass velocity or temperature are uncommon in the software world. Instead we attempt to derive a set of indirect measures that lead to metrics that provide an indication of the quality of some representation of software. Because software measures and metrics are not absolute they are open to debate. Fenton FEN91 addresses this issue when he states Measurement is the process by which numbers or symbols are assigned to the attributes of entities in the real world in such a way as to define them according to clearly defined rules. . . . In the physical sciences medicine economics and more recently the social sciences we are now able to measure attributes that we previously thought to be unmeasurable.Of course such measurements are not as refined as many measurements in the physical sciences . . . but they exist and important decisions are made based on them . We feel that the obligation to attempt to measure the unmeasurable in order to improve our understanding of particular entities is as powerful in software engineering as in any discipline. QUICK LOOK What is it By its nature engineering is a quantitative discipline. Engineers use numbers to help them design and assess the product to be built. Until recently software engineers had little quantitative guidance in their work but that s