Every decision has a different level of influence or impact in the human life. Very often, numerous smaller decisions have to be made before a complex decision can eventually arrive at its best conclusion. Moreover, each decision may have a bearing on other subsequent decisions, and thus requires the decision making process to be structured in such a flexible manner that enables the decisions to be considered and solved differently each time. However, most decision making processes and systems are designed to solve simple and linear problems and are therefore unable to support complex problems which consist of interrelated decisions that span across multiple domains, paradigms, and/or perspectives. Furthermore, the true purpose of decision making is to gain a better understanding of the issues involved behind each decision. To address these problems we first proposed conceptual decision-making and modelling processes, and then developed and implemented a flexible object-oriented decision system framework, architecture, and prototype to support these proposed processes. Through the implementation, we were able to explore and implement some general modelling ideas as well as specific issues such as the integration of models and scenarios of different types, levels of complexity, depths of integrations, and decision maker orientations.