1. Modeling
Shari L. Pfleeger and Joanne M. Atlee, Software Engineering: Theory and Practice, 4th edition, Prentice Hall, 2009.
Hans Van Vliet, Software Engineering: Principles and Practice, third edition, John Wiley & Sons, 2008.

2. What Is a Model?
Pairs (2 minutes)

3. Models
‘Complete’ meaning no additional information is needed to understand the system from that perspective
abstraction of some entity
understand before build
omits nonessential details
examples:
architectural models to show customers
airplane scale models
storyboards of advertisements
outlines of books

4. Different Models
Several models will be considered in developing our system
Use case model: describes requirements from the user perspective
Design model: describes classes and objects
Implementation model: source code
Test model: test cases and test procedures

5. Investigate: People and machines playing some role (actors)
Items produced, consumed, or modified
Functions performed
Modes of operation that determine when functions are performed

6. Analysis All aspects of the problem domain need to be investigated.
Decompose the problem into smaller problems until the entire problem is fully understood.
The models that depict information, function, and behavior must be constructed in a manner that uncovers detail.

7. Note:
"Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful.";
"Essentially, all models are wrong, but some are useful."
George E.P. Box & Norman R. Draper, Empirical Model-Building and Response Surfaces (Wiley 1987) pp. 74 and 424. (Professor of statistics, U of Wisconsin)

8. Purposes of a Model: Testing a real entity before building it
Communication with customers
Visualization
Reduction of complexity

9. Operational Principles: Analysis Methods
The information domain of a problem must be represented and understood.
The functions that the software is to perform must be defined.
The behavior of the software (as a consequence of external events) must be represented.

10. Modeling Views It all comes down to these: Objects: data
Functions: transformations of data
States: transitions controlling transformations

11. Data (Static) Models
Used to understand the data and actors in a system
Abstraction of the information needed and generated by the system
Describes the problem domain
Helps identify, classify, and abstract the problem

12. Function (Transformational) Models
Used to understand the transformations that take place in the system
Used to understand the inputs and outputs for computations

13. State (Dynamic) Models
Used to understand states and modes of the system
Used to specify the flow of control through the system and system components

14. Modeling Functional Model – transformational, “function” aspects of
system
Data
Dictionary
Object Model - static,
structural, data aspects
of system
E-R
Diagram
Data-flow
Diagram
Class
Diagram
State-Transition Diagram
Decision Tables
Collaboration Diagram
Dynamic Model - temporal,
behavioral, “control” aspects
of system

15. Static Models
Entity Relationship Models
Class Models

16. Dynamic Models Event trace Message sequence chart
Show a sequence of events and associated responses
Message sequence chart
Enhanced event trace notation
Vertical lines are entity time lines (time flows from top to bottom)
Horizontal lines are messages or events

17. Dynamic Models (Cont.) State Machines
Should remind you of FSMs from theory.
Nodes are states
Arcs are transitions
Event (condition)/action
Instantaneous
Statecharts: UML state machine notation

18. Functional Models Data Flow Diagrams Processes Data Data store
Use Cases

19. Static Models Pairs (10 minutes) What are the nodes (node types)?
Read about ER diagrams PP
What are the nodes (node types)?
What are the edges?

20. In Class: Diagram the Following
A library has books and journals, and each can be checked out.
A patron has a name, a UTEP ID number, an address.
A patron can check out any number of books or journals.
When a book or journal is checked out, it must be returned in 5 days (so we must keep track of the checkout date)

21. In Class: Static Models
Show how you can use an ER diagram to represent
Association
Aggregation
Generalization
Composition
role names
multiplicities