A. Analysis of Expert System Development In developing an ES, it is important for us to know that the criteria that are need to build a successful system. A system is considered successful when it can perform tasks as intelligence as human thinking and also it has the nature of intelligence [7]. In addition, cost of building an ES is always a concern for vendor to take in considerations, so it is important that error to made can be minimize to the lowest in order to save cost. As market demand, a user friendly expert system has slowly become a need because a user friendly system will save time and effort for end user when they first time expose to the system [7].