Though a lot of achievements, which mainly based on theory, have been obtained, many problems remain unsolved for their complex nature. .

• 由于面向对象系统中的依赖关系与诸多因素相关，使问题研究起来比较复杂，目前的研究成果主要是基于理论上的研究，还不能完全满足实际的需要。