Better human machine cooperation is based on human trust in the machine. It has not been established, however, the system design which assures the machine is trusted by human operators in an appropriate manner. This is because the notion of trust is still vague since it has several aspects. The paper proposes to adopt a human-machine cooperation framework that the authors have developed. Based on the human-machine cooperation framework, each aspect of trust is identified. Examples are given to help readers understand each aspect.