Com S 362 Lecture Notes for Sep 11
System Sequence Diagrams

Reading: Larman Chapter 10

Remember: Software Process Models, Requirements, 
Specification, Requirement Elicitation, Use Cases,
Scenarios, Actors, Type of Actors: Primary, supporting,
offstage. Domain models, concrete classes, associations,
attributes

Recap:

Domain Model:

When: Often constructed during object-oriented analysis

Why: Understandability, and helps lower representational 
gap between domain and software

What: A visual representation of conceptual 
classes or real-situation objects in a domain. 

Consists of: Conceptual classes, Attributes, Association 
between these conceptual classes

Today's Lecture:

Associations Multiplicity Clarification:

* - Zero or more
1..* - One or more
1..40 - One to 40
5 - Exactly five
3,5,7 - Exactly 3, 5, or 8

Description classes: (Meta-class) - Contains information 
that describes something else. 

For example:

Book Description 1--Describes---* Books

(In this case, there many copies of the same title and the
book description describes them all.)

Product Description 1--Describes---* Item

Refinement Steps in S/W Development:

At each stage in the S/W development process, we 
are refining the artifacts created in the previous 
stage, until the artifacts are refined to the 
extent to be executable.

**START** Domain and the problem in the domain -> 

Analysis of domain and the problem in the domain -> 

Terse description (in form of use cases) of how the 
problem will be solved by the system by fulfilling 
each required goal. In the requirement analysis 
phase, we wrote use cases. Remember - Use Case = 
[Scenario = [Actor -fulfill--> Goal]]* ->

Construct detailed static description of the domain
a.k.a Domain Models, Describes actors and other 
conceptual classes in the system in more detail ->

Construct detailed dynamic description of the each 
use case scenarion a.k.a. System sequence diagrams.
Describes interaction between actors and system 
in more details ->

Translate a subset of domain model to classes and 
objects in the system (create class diagrams),
add more classes representing objects inside the
system ->

Translate a system sequence diagram to interaction
between domain and between system classes (create
interaction diagrams) ->

Produce an implementation from the class diagrams 
And the interaction diagrams, verify validate ->

**END** Final software product. 

System Sequence Diagram:

In the domain model, we studied the static relationships
in the system. However, dynamic nature of actor-system 
interaction is also important. System sequence diagram is a
detailed representation of the steps of interaction between
the actor and the system to fulfill a goal.

For example, a goal in the library administration system
was to checkout a book

Actor [Patron] --Goal [Checkout] --> System

We can describe the steps in the fulfillment of 
this goal in more detail.

Actor [Patron] -- Scans membership card --> System

Actor [Patron] <-- Accepts/Rejects -- System
                   membership card 

Actor [Patron] -- Scans book --> System

Actor [Patron] <-- Prints receipt -- System
                   of checkout/due date