| simple sequence diagram | lifeline | a label if its meaning is not obvious, using a caption or pop-up label that appears when the user moves the mouse over it | the dynamic aspects of a software system |  better than collaboration diagram when:-  You want the reader to be able to easily see the order in which messages occur
 -  You want to build an interaction model from a use case
 -  You need to show details of messages, such as parameters and return values 
 
  | it conveys or summarizes complex concepts or mechanisms more  easily than other techniques | sequence diagram | 8.1 - Interaction Diagrams | objects from left to right across the diagram with an actor that initiates the interaction often shown on the left | aspects of the architectural model | to better understand the sequence of messages | developing a class diagram and a use case model because you need to know the actors and objects involved in an interaction | - can be hard for users to interact with or interpret
 - not usable by blind people
 - it can be expensive to program diagram drawing software 
 
  | note | to define the protocol used when two components communicate with each other | you to visualize how the system runs | a collaboration diagram | time as the vertical dimension with time progressing downwards to the bottom of the diagram | the sequence of messages exchanged by the set of objects (and optionally an actor) performing a certain task | more or less detail depending on what you wish to communicate | Unified Modelling Language |