Software Design, Verification and Validation：软件设计，验证和确认.ppt

les * * Software Design, Verification and Validation Elements of a Code Integrity Management System for Real-time Embedded Systems Joao H. Silva, Ph.D. jsilva6@ joaosilva@ Problem Definition Typical Scenario: 1 Senior Manager ? 178 – 200 project releases 2 releases with major Problems 176 releases without any major problem Question: How do we anticipate those two “Bad Releases” before they become a problem Consider These Statistics Statistic #1: For every thousand lines of code developed by software engineers, there could be as many as 20 to 30 defects on average Statistic #2: In 2003, Developer News reported 50 percent of all bug fixes are incorrectly performed the first time, often introducing new bugs in the fixing process Statistic #3: As bugs progress through the development cycle, defects found become exponentially more expensive to fix – it is at least 30 times more costly to fix software in the customer versus during development – SEI 2001 For automotive releasing a bug into the field may promote a very costly recall of that vehicle(s) Software Defects Software defects are inevitable. “…people who write software are human first and programmers only second – In short, they make mistakes, lots of them...” The Economist 2003 Where is the complexity? Avionics Boeing 747 ? 0.4 M LOC Boeing 777 ? 4 M LOC Technology Review 2002 Automotive 2010 Premium ? 100 M LOC 1995 – 2000 ? 52%/Year 2001 – 2010 ? 35%/Year Tony Scott, GM CIO Use of Models CMM CMMi Complexity Models Metrics Maturity Model TMM –Testing Maturity Model Others A model to understand complexity PROBLEM HW Solution #1 SW Solution #1 COMPLEXITY HW/SW Co-Design Size Error Proneness Quality Solution #1 Usability Reliability Change Productivity Solution #1 Maintainability MIPS Understandability EFFORT What influences the complexity of SW? Size Module length Tools Language Features Management Reuse Outsourcing Unnecessary functionality Etc… Error-Proneness Environment Competence Methods U