在软件的整个生命周期当中，软件维护占有大的一部分。基本上可以分成四个类别：

• 适应性维护：处理变更和适应环境变化
• 增强性维护：功能增强
• 矫正性维护：错误处理
• 预防性维护：提高可维护性，防止后续出现问题

有调查表明，有75%的维护时间花在一两种类别上，而有21%的时间花在错误修正的维护上。那么怎么样来提高软件的可维护性呢，以下是利于增强维护的几个方面：

维护因子(Maintenance Factors)                             所占比重(PlusRange)

维护专家(Maintenance specialists)                          35%            

职员经难丰富(High staff experience)                        34%            

基于表格的变量和数据(Table-driven variables and data)      33%            

基准代码低复杂度(Low complexity of base code)              32%            

专业搜索引擎(Y2K and special search engines )              30%            

代码重构工具(Code restructuring tools )                    29%            

再工程工具(Re-engineering tools )                          27%            

高级语言(High level programming languages )                25%            

逆向工具(Reverse engineering tools)                        23%            

复杂分析工具(Complexity analysis tools)                    20%            

错误跟踪工具(Defect tracking tools)                        20%            

块更新(Y2K “mass update” specialists)                      20%            

自动化变更控制工具(Automated change control tools )        18%            

无偿加班(Unpaid overtime)                                  18%            

质量度量(Quality measurements )                            16%            

正式的基准代码检查(Formal base code inspections )          15%            

回归测试组件(Regression test libraries)                    15%            

优秀的响应时间(Excellent response time)                    12%            

大于10天的年度培训(Annual training of > 10 days )          12%            

较高的管理经验(High management experience )                12%            

自动化的帮助(HELP desk automation )                        12%            

无错误的模块(No error prone modules )                      10%            

在线错误报告(On-line defect reporting )                    10%            

生产力度量(Productivity measurements)                      8%             

易用(Excellent ease of use)                                7%             

用户满意度(User satisfaction measurements )                5%             

高团队士气(High team morale )                              5%             

----------------------------------------------------------------------------------------

合计(Sum)                                                  503%   

 

 

而不利于系统维护性的因素如下:

 

Maintenance Factors	Minus Range
Error prone modules	-50%
Embedded variables and data	-45%
Staff inexperience	-40%
High code complexity	-30%
No Y2K of special search engines	-28%
Manual change control methods	-27%
Low level programming languages	-25%
No defect tracking tools	-24%
No Y2K “mass update” specialists	-22%
Poor ease of use	-18%
No quality measurements	-18%
No maintenance specialists	-18%
Poor response time	-16%
No code inspections	-15%
No regression test libraries	-15%
No help desk automation	-15%
No on-line defect reporting	-12%
Management inexperience	-15%
No code restructuring tools	-10%
No annual training	-10%
No reengineering tools	-10%
No reverse-engineering tools	-10%
No complexity analysis tools	-10%
No productivity measurements	-7%
Poor team morale	-6%
No user satisfaction measurements	-4%
No unpaid overtime	0%
Sum	-500%

 

原文见:

http://en.wikipedia.org/wiki/Software_maintenance