1. Solving the Problem
Analysis & Design

2. Requirements Phase Requirements -- should be an unambiguous description of the external behavior of the system to be built
Typical problems :
Contains embedded design decisions (How vs. What).
Vague (must be measurable / testable)
Computer industry language (instead of user's language)
Requirements are not traceable to the system developed

3. Analysis Phase Discover and understand the problem domain
Object-oriented Analysis
decompose a problem by selecting relevant concepts from the vocabulary of the domain.
Develop a Conceptual Model
include class and interaction diagrams.

4. Conceptual Model
contains important real-world concepts and associations in the vocabulary of the problem domain: includes objects, roles, events, interactions
becomes the foundation for the class model

5. Use Cases A purposeful user interaction with a system
A narrative description of a sequence of actions required to produce something of value to an actor or organization

6. Use Cases describe functional requirements of the system
give a clear description of needed system behavior
help customer and developer agree on what the system should do
provide a basis for performing verification tests.
trace requirements to actual classes and operations in the system.
set bounds on the problem space

7. High-level use cases (collected to determine the complete scope of the system)
Use Case – the name is usually a business or domain process (Order a product, register for courses)
Actors -- external agent (person playing a role, computer system, input/output device)
Type -- primary, secondary or optional
Description -- a short narrative description (2 - 3 sentences)

8. Setting Priorities (rank order use cases)
Ranking may involve a combined score including multiple factors:
Impact on the architectural design
Risky, time-critical, or complex functions
New or risky technology
Represent line-of- business processes
Directly support increased revenue or decreased costs.
Or ranking may simply classify use cases as high, medium, or low
The most important use case is then expanded

9. Expanded Use Case (minimal technology references)
Buy Items (essential description)
Typical Course of Events:
Actor Actions:
System Response:
1) This use case begins when a Customer arrives at a cashier's location with items to purchase
2) The Cashier records the identifier from each item, its description and price from the sales tag. If there is more than one of the same item, the Cashier can enter the quantity
3) Multiply the price by the quantity and add this to the ongoing sales transaction
4) When the item entry is complete,
5) Calculate the sales total
6) Cashier tells the Customer the total
7) Customer gives cash payment.
8) Cashier records the cash received amount
9) Calculate balance due the customer

10. Object Oriented Design (OOD) Phase
Developer decides how the system will be implemented
Many of the concepts become classes
The design phase elaborates (adds attributes and methods) to the class model
Try this technique
Modify the use case to include new system features

11. Put new system features into the use case
Buy Items (system solution)
Requirements:
R1, R2, R3, R4, R5, R6
Actor Actions:
System Response:
1) This Use case starts when a Customer arrives at POST with items to purchase.
2) The Cashier enters UPC of each item.
3) Use UPC to determine item name, price and description. The item price is added to the sales total.
If there is more than one of an item, the Cashier can enter the quantity as well or re-enter the UPC
Show description and price of the current item
4) On completion of item entry, the Cashier indicates to the POST that item entry is complete.
5) Calculate and present the sales total.
6) The Cashier tells the customer the total
7) The Customer chooses payment type:
8) Log the completed sale
a.       If cash, see Pay by Cash
9) Update inventory levels
b.      If credit, see Pay by Credit
10) Generate a receipt
c.       If check, see Pay by Check
11) The Cashier gives the receipt to the Customer
12) The Customer leaves with the items purchased.

12. Design a User Interface for the user

13. Use screen navigation diagrams when necessary

14. Plan the first Iteration
Determine how much can be delivered within the first development cycle
If necessary, create a simplified use case to fit the first time-box

15. Special Considerations for the first Development Cycle
Try to handle the most difficult parts of the system first.
If the architecture is untested, exercise the functionality of the architecture.
If there is technological risk, exercise all the significant interfaces and interactions among subsystems to assure they are compatible.

16. Architecture – describes the structure of software systems
Architecture is the set of significant decisions about the organization of a software system, the selection of the structural elements and their interfaces.
Describe major subsystems
External software interfaces
User interface
Database organization
Data storage
Key algorithms
Concurrency
Security
Networking
Portability
Programming language
Error handling

17. Plan Future Cycles In subsequent development cycles,
add functionality to the previously delivered use case or do another use case
update task assignments and milestones for each cycle:
Requirements
Design
User documentation
Test cases
Technical reviews
etc

18. First Cycle: Simplified Use Case
Buy Items with cash (First Iteration)
Actor Actions:
System Response:
1) This Use case starts when a Customer arrives at POST with items to purchase.
2) The Cashier enters the UPC and quantity of each item.
3) The item name and description is displayed. The price is added to the sales total.
4) On completion of item entry, the Cashier indicates to the POST that item entry is complete.
5) Presents the sales total.
6) The Cashier tells the customer the sales total
7) The Customer gives a cash amount equal to or greater than the sales total
8) The Cashier enters the cash amount
9) Calculate and display change due the customer
10) Generate a receipt
11) The Cashier gives the receipt and change due to the Customer
12) The Customer leaves with the items purchased.

19. Make a minimum conceptual model
concepts relevant to the use case being developed.
A complete conceptual model would be all significant real-world concepts in the problem domain.

20. Find domain concepts in the use case
Who are the actors and what are they trying to do?
What “real world” objects are needed for each use case?
How do the objects work together to complete each use case goal?
Consult with domain experts
Parse for noun and verb phrases
Nouns become objects or attributes
Verbs become operations or associations.
Use a Concept Check List

21. Concept Check List (Craig Larman)
Physical objects
Specifications, designs or descriptions of things
Places
Transactions
Transaction line items
Roles
Things in a container
Containers of other things
Catalogs
Events
Organizations
Processes
Rules and policies
Records of finance, work, contracts, legal matters
Financial instruments and services
Manuals, books
External Computer Systems or devices
Abstract noun concepts

22. Concept Diagram of Buy Items

23. Decide which domain concepts become objects that implement a solution
Try CRC cards to Bridge from Concepts to Classes CRC cards (Class, Responsibility, Collaboration)
Original paper by Beck and Cunningham at

24. CRC Cards Class Name -- Domain concept or programmer created class
Class Name = Sale
Responsibilities:
Collaborators:
  store Item specs and quantity
  SalesLineItem
calculate a sales total 
store payment amount and type
Class Name -- Domain concept or programmer created class
Responsibilities -- Tasks an object can do alone because of its local knowledge
Collaborators -- Tasks done by other objects because of their knowledge

25. Responsibility Responsibilities become class methods
The method accomplishes a task by the object acting alone or with the help of others.
Two Basic Responsibilities for objects
Knowing
object’s awareness of its own data, its links to other objects and knowledge it can derive or calculate
Doing
objects ability to modify itself, create and link to other objects, or delete other objects and links, command other objects to take action or control or coordinate activity in other objects

26. CRC Card Procedure
Create cards for each relevant object in the use case
-- actors initiating a message to the system
-- the first object that receives the message
-- every object from the domain used in the solution
Walk through the handling of a system event
Allocate responsibilities by deciding which class handles an event or delegates it to another object
-- Put the main responsibilities of each class on the card.
-- Put the collaborators of each class on the card

27. Role Play the Class
A designer or member of a group can act the part of a "Class" when it is given control in a scenario
When role playing a class, determine
what can you do,
how are you dependent on others

28. Scenarios
Each use case has a successful outcome and usually one or more failure outcomes.
Failures usually are:
Looking for an object which does not exist (identifier not found)
Creating a new object but the identifier already exists.
Violation of business rules (i.e. Customer withdraws an amount that makes the balance lower than the minimum required by the bank)
Use scenarios to validate the responsibilities of each object.
Events leading to failure and to success

29. Use truth tables to check for completeness
Use Case Scenarios
Buy Items 1 2 3
Pre-Conditions
UPC Exists F T
Customer has sufficient funds
Post-Condition Actions
Reject sale and provide a message X
Accept transaction

30. Class Diagram

31. Interaction diagrams (sequence)

32. Interaction Diagrams (collaboration)

33. Entity-Relationship Diagrams

34. Free Information for UML and ER diagramming
Introduction to UML Diagramming
Introduction to ER Diagramming