lecture set 3e introduction basic software development issues 1. notes on software development 2....
TRANSCRIPT
Lecture Set 3E
Introduction Basic Software Development
Issues
1. Notes on Software Development2. Intro to Software Development
Tools 7/31/2008 2:43PM
Slide 2
Objectives
Explain the software development life cycle
Describe selected tools used to help design software systems
Develop some ability to use UML Activity Diagrams in mapping out the behavior of a software system
Slide 3
Introduction to Software Development
The software development life cycle consists of a sequence of well-defined steps Problem identification System design System implementation System documentation System testing System deployment Postimplementation audit
Missing from this “picture” are the “feedback” loops (What does this mean?)
Slide 4
Software Design Methodologies and Tools
Software systems should be designed before they are implemented
As software systems become more complex, the design process becomes increasingly important
Several methodologies exist to design software systems The choice of methodology is often
subjective Design tools apply some type of model to
describe the software system
Slide 5
System Analysis Methodologies
Pseudocode uses English-like statements to depict an application’s actions
Top-down design is used to subdivide general tasks into more specific tasks
Flowcharting uses graphical symbols to depict an application’s actions
The Unified Modeling Language (UML) supplies several graphical templates to model a system
Slide 6
Pseudocode
Pseudocode uses English-like statements to describe a particular task
Pseudocode is not exact Different developers may write pseudocode
differently Pseudocode characteristics
The words “start” and “stop” denote the beginning and end of a process
The word “if” indicates a decision Decisions can be nested
Pseudocode used mainly for small algorithms design – sorts, searches etc
Slide 7
Top-Down (Hierarchical) Design
Steps Define general tasks first Decompose general tasks into more
specific tasks Continue decomposing sub-tasks, as
needed Hierarchical Input Process Output
(HIPO) charts are used to visualize the top-down design process
Slide 8
HIPO chart for an ATM withdrawal
Slide 9
Expanded HIPO chart
Slide 10
Flowcharting
A flowchart consists of graphical symbols that depict the processing in an application or part of an application – you’ve seen these before
Each graphical symbol denotes a specific type of operation
Flowcharting also most suitable for small algorithms design – not for modeling more complex systems
Even this ATM model is not quite accurate
Slide 11
Generic flowchart
Slide 12
ATM withdrawal flowchart
Slide 13
The Unified Modeling Language (UML)
The Unified Modeling Language (UML) is used to model complex software systems in a visual way
It's one of the premier design methodologies in use today
The UML consists of several diagrams to model specific parts of a system
Most important because it facilitates modeling of data and processes together
Slide 14
Common UML Diagrams
Class diagrams model the conceptual and physical aspects of a system
Use case diagrams model the actors (users) of a system
Activity diagrams show the actions performed by the system and the order in which those actions are performed UML activity diagrams are similar to
flowcharts
Slide 15
UML Class Diagrams
UML class diagrams are made up of three sections The top section contains the name of a
class The middle section contains the attributes
of a class (data) The operations (class methods) appear in
the bottom section The data passed to an operation appears in
parentheses
Slide 16
UML Class Diagram
Slide 17
UML Use Case Diagrams
Use case diagrams model the actors (users) of the system A rectangular box defines the boundaries
of the system Stick figures define the actors Lines connect the actors with the system's
elements We will not get too wrapped up in this
aspect of UML until near the end of the course
Slide 18
UML Use Case Diagram
Slide 19
UML Activity Diagrams
UML activity diagrams resemble a flowchart
A solid black circle at the top of the diagram represents the activity’s initial state
Arrows connect activities together A horizontal bar represents a decision
In UML terms, this is called a fork transition
A bordered black circle represents the activity's ending state
Slide 20
UML ActivityDiagram
Slide 21
“Relaxed” Activity diagram
Activity diagrams hold the key to our projects.
You will need to use them in understanding the behavior of the systems you will build ATM project Game project Transaction Processing project
I will use a relaxed version of an activity diagram (a behavior diagram) in class
8/13/2008 10:35 PM