Sequence diagram has many meanings and usages. In biology, sequence diagram can be referred to as the physical map of nucleotide sequence on genetic material. It is the most basic work in the human genome project. It is the highest level and most detailed physical map of human genome at the molecular level. It measures the genomic DNA sequence with a total length of 1m and consists of about 3 billion pairs of nucleotides. In software engineering, sequence diagram is a representation of object interaction. UML model can be divided into two types: dynamic model and static model. Use case diagram, class diagram and object diagram are static structural models in UML. One of the dynamic models of UML system is interaction view, which describes the sequence of messages passing between the roles of the system. Sequence diagram is a form of interactive view. Sequence diagrams are primarily used to show these interactions between objects in the sequence in which they occur. Much like class diagrams, developers generally think that sequence diagrams only make sense to them. However, business people in an organization will find that sequence diagrams show how different business objects interact, which is useful for communicating how the current business is going. In addition to recording the organization's current events, a business level sequence diagram can be used as a requirements document to deliver requirements for a future system. In the requirements phase of a project, analysts can take use cases to the next level by providing a more formal level of expression. Sequence diagram is composed of object, lifeline, activation, messages, branch and subordinate flow