Software Development Process Yonglei Tao

Software Development Tasks Solutions Conceptualization Communication Coordination Solutions Processes and methodologies for analysis and design UML for communication and coordination Tools that automate or support methodology steps.

Software Process A software process defines a series of activities performed to construct a software system Each activity produces some artifacts, which are the input to other phases Each phase has a set of entrance criteria and a set of exit criteria

The Waterfall Model System Engineering Software Requirements Analysis Software Design Coding & Unit Testing Integration & Integration Testing Acceptance Testing Maintenance

Merits of the Waterfall Model Simplifies project management Supports function-oriented project organization Each project is carried out by a pipeline of functional teams Each functional team is specialized in one function such as requirements analysis, design, implementation, integration and testing, and so forth

Problems of the Waterfall Model It is inflexible to requirements change The long development duration means the system is outdated when it is delivered Users cannot experiment with the system to provide early feedback The customer has to wait until the entire system is implemented and deployed to reap the benefits The customer may lose the entire investment if the project fails

Software Process Models Prototyping Process Model Evolutionary Process Model Spiral Process Model Unified Process Model Personal Software Process Model Team Software Process Model Agile Process Models

Agile Processes Agile development values Agile processes emphasize individuals and interactions over processes and tools working software over comprehensive documentation customer collaboration over contract negotiation responding to changes over following a plan Agile processes emphasize teamwork joint application development with the user design for change rapid development and frequent delivery of small increment in short iterations

Agile Process Models phases in an iteration Iterations

Some Well-Known Agile Methods Dynamic Systems Development Method (DSDM) Feature Driven Development (FDD) Scrum Extreme Programming (XP) Crystal Clear Lean Development

Agile versus Plan-Driven Agile methods work well for small to medium-size projects that face frequent changes in requirements Plan-driven approaches remain the de facto choice for large, complex systems where predictability is important Both are needed “The challenge is to balance the two approaches to take advantages of their strengths and compensate for their weaknesses.” – Boehm and Turner

Process and Methodology Defines a framework of phased activities Specifies phases of WHAT Does not dictate representations of artifacts It is paradigm-independent A phase can be realized by different methodologies Methodology Defines steps to carry out phases of a process Describes steps of HOW Defines representations of artifacts (e.g., UML) It is paradigm-dependent Steps describe procedures, techniques, and guidelines

Software Design Paradigms Include a set of theories, standards, and methods A way to organize knowledge A perspective to view a software system Also provide notations, guiding principles, evaluation criteria, and support tools

(1) Structured Analysis and Design SA / SD SA uses Data Flow Diagrams (DFDs) SD uses Structure Charts View point Functional What needs to be done Design strategy Top-down decomposition

Data Flow Diagrams

Problem Solving

DFD Example - Context Diagram

Level 1 DFD

Level 2 DFD

Structured Design – Structure Charts

From Analysis to Design

Structure Chart

A Travel Agency Booking System

(2) Jackson System Design JSP / JSD JSP does not address issues of modularity, but JSD does View point How input and output data are organized A program structure reflects the structure of what to be processed Design strategy Compositional

Jackson System Programming D C B (a) H L M o (b) X Y * (c)

Example - A Gas Station System

Step 1: Draw a Structure Diagrams for I/O

Step 2: Merge Structure Diagrams to Form the Program Structure Diagram

Step 3: Allocate Operations to Elements of the Program Structure Diagram

Steps 4 & 5: Create a Textual Description of the Program Structure Diagram

(3) Object-Oriented Design A different way of viewing the world

Object-Oriented Concepts Agents and communities Classes and objects Responsibilities Object interaction Computation as simulation Using the application domain as a metaphor

Methodology in the Textbook It is designed for beginners as well as seasoned developers. It is aimed at educating software architects and systems analysts. It can be applied to agile as well as plan-driven projects. It has been applied to industrial projects Many students continue practicing the methodology after graduation

Methodology Overview – Planning Phase Business goals & needs Current situation Acquiring Requirements & Domain Modeling Requirements Deriving Use Cases from Requirements Abstract & high level use cases, use case diagrams Allocating Use Cases & to Iterations Use case-iteration allocation matrix Producing an Architecture Design Software architecture

Methodology Overview – Iterative Phase Software architecture Use case-iteration allocation matrix Accommodating Requirements Change Iteration use cases Domain Modeling Domain model Actor-System Interaction Modeling & UI Design Domain model Expanded use cases & UI design Behavioral Design Behavior diagrams Deriving Design Class Diagram Design class diagram TDD, Integration, & Deployment