The software community faces a major challenge that is raised by fast growing demand for rapid and cost effective development and maintenance of large scale and complex software systems. To overcome the challenge, the new trend is to adopt component based software engineering (CBSE). The key difference between CBSE and traditional software engineering is that CBSE views a software system as a set of off-the-shelf components integrated within an appropriate software architecture. CBSE promotes large scale reuse, as it focuses on building software systems by assembling off-the-shelf components rather than implementing the entire system from scratch. CBSE also emphasizes selection and creation of software architectures that allow systems to achieve their quality requirements. As a result, CBSE has introduced fundamental changes in software development and maintenance.