1. Systems Analysis and Design in a Changing World, Thursday, Feb 22

2. Today’s Schedule Using Events for Requirements
Using “Things” for Requirements
For Tuesday, February 27 Finish Reading Chapter 5, ERDs and Class Diagrams
Try out ERDs in Visual Paradigm

3. Recall … Where You Are Headed

4. Events Affecting a Charge Account Processing System that Lead to Use Cases

5. Identifying Events Can be difficult to determine
Often confused with conditions and responses
May be useful to trace a transaction’s life cycle
Certain events left to design phase
System controls to protect system integrity
Perfect technology assumption defers events

6. Sequence of “Transactions” for One Specific Customer >> Many Events

7. Defer Some Events Until Design

8. Event Table: Catalog of Information about Each Use Case
How do the “events” in Activity Diagram fit?

9. “Things” in Problem Domain
Define system requirements by understanding system information that needs to be stored
Store information about things in the problem domain that people deal with when they do their work
Analysts identify these types of things by considering each use case in the event table
What things does the system need to know about and store information about?

10. Types of Things

11. Developing an Initial List of Things
Step 1: Using the event table and information about each use case, identify all nouns
Step 2: Using other information from existing systems, current procedures, and current reports or forms, add items or categories of information needed
Step 3: Refine list and record assumptions or issues to explore

12. Questions for Refining List
Should you include it?
A unique thing system needs to know about?
Inside scope of this system?
Need to remember more than one of these?
Should you exclude it?
Synonym for another thing already in list?
Is it really an output?
Input that results in recording info already in list?
Should you research it?
Is it a characteristic of another “thing”?
What if assumptions change, is it still needed?

13. “Things” have … Relationship Attribute (characteristic)
Naturally occurring association among specific things
Occur in two directions
Number of associations is cardinality or multiplicity
Binary, unary, ternary, n-ary
Attribute (characteristic)
One specific piece of information about a thing

14. Cardinality/Multiplicity of Relationships

15. Identifier or Key – Attribute that Uniquely identifies the “thing”
Attributes and Values
Identifier or Key – Attribute that Uniquely identifies the “thing”

16. Data Entities
Things system needs to store data about in traditional IS approach
Modeled with entity-relationship diagram (ERD)
Requirements model used to create the database design model for relational database

17. Objects
Objects do the work in a system and store information in the object-oriented approach
Objects have behaviors and attributes
Class – type of thing
Object – each specific thing
Methods – behaviors of objects of the class
Objects contain values for attributes and methods for operating on those attributes
An object is encapsulated – a self-contained unit

18. Data Entities Compared with Objects (Figure 5-22)

19. The Entity-Relationship Diagram (ERD)

20. Cardinality Symbols of Relationships for ERD

21. Expanded ERD with Attributes Shown

22. Customers, Orders, and Order Items

23. ERD with Many-to-Many Relationship

24. Many-to-Many Relationship Converted to Associative Entity to Store Grade Attribute

25. RMO Customer Support System ERD (Figure 5-29)

26. Now you try it …
Case Study: (Page 194-5) The Spring Breaks ‘R’ Us Travel Service Booking System
#1 Events and event Table
#2 Data Entities and their relationships

27. For Tuesday, February 27
For Tuesday, February 27 Finish Reading Chapter 5, ERDs and Class Diagrams
Try out ERDs in Visual Paradigm