Interaction Diagrams:

System Sequence Diagram

5.1 Introduction

Interaction diagrams describe how groups of objects collaborate in some behavior. An interaction diagram typically captures the behavior of a single use case. Interaction diagrams do not capture the complete behavior, only typical scenarios.

5.2 Objectives

• Better understanding of the interaction diagrams.

• Get familiar with system sequence diagrams.

• Practice drawing the interaction diagrams using Sybase Power Designer.

5.3 Tasks

1. From the analysis in lab 2, identify the key functional requirements.

2. Create a System Sequence Diagram that represents the functional requirements for the intended information system of WAIPS;

5.4 Milestones

Below are the milestones (specific goals) to aim for during this week of the project. The intention is to tie in with coverage presented in lectures and tutorials. You will receive further milestones in subsequent weeks on Blackboard as well as other helpful information.

Milestone	X
1. You should use these techniques to create sequence diagrams for your Project.
2. To have read and understood requirements of the case study

5.5 Suggestions

The following suggestions are provided to help students start the task:

5.5.1 Analysing a Systems Behavior

System sequence diagrams (SSDs) show the inputs and outputs for each use case as messages

5.5.2 Sequence Diagrams

• Only shows actor and one object
• The one object represents the complete system
• Shows input & output messaging requirements for a use case

• Actor, :System, object lifeline
• Messages

5.5.3 Creating Sequence Diagrams

1. Identify input message
   12. See use case flow of activities or activity diagram
2. Describe the message from the external actor to the system using the message notation
   12. Name it verb-noun: what the system is asked to do
   13. Consider parameters the system will need
3. Identify any special conditions on input messages
   12. Iteration/loop frame
   13. Opt or Alt frame
4. Identify and add output return values
   12. On message itself: aValue:= getValue(valueID)
   13. As explicit return on separate dashed line