Sequence diagrams are used to model the flow of messages, events and actions between the objects or components of the system. Sequence diagrams are typically used for the system at the stage of under development. This is why sometimes sequence diagrams are called as ‘event scenarios’. Sequence diagram involves classes and objects. All the interactions between them are arranged in time sequence depicted as vertical lines called ‘lifelines’. Horizontal arrows are the messages exchanged between them and its order of sequence. Solid arrow heads and open arrow heads are represented as synchronous and asynchronous messages respectively and dashed line represents reply messages.
There are few aspects which made Sequence diagrams more significant as follows:
# Sequence diagrams are very useful in complex interaction between the components of the system. These are often used to design interaction between different components that need to work as team in order to accomplish the task. These are particularly useful when the components of system or being developed by different teams in parallel.
# In web-based systems like distributed systems, sequence diagrams performs vital role in documentation and validation of the architecture, interface and actual logic of the each component of the system.
# Usage scenario describes a way of system used by its actors. Sequence diagram can be used to separate the details of the each use-case by visual representation of the system in particular scenario. Which helps to describe the expected behavior of the system and contributes a strong foundation in development of the system architecture.