Software Development Process Models

Question 1

Process

Answer 1

A process is a series of actions bringing about a result

Question 2

Software Development Process

Answer 2

1. The process by which user needs are translated into software product. The process involves
   - translating user needs into software requirements
   - transforming the software requrirements into design
   - implementing the design into code
   - testing the code
   - and sometimes, installing and checking out the software for operational use
2. May overlap

Question 3

Software Process Model

Answer 3

1. A (software) process model is
   - an abstraction of similar software processes
   - a blueprint (a pattern) used to organize and perform a software process
2. A software process model should be
   - useful and helpful
   - clearly defined
   - accepted by the development organization
3. Reduction of project risks!

Question 4

Code and Fix

Answer 4

• Coding and error correction together with ad-hoc tests are the only activities performed consciously
• Systems dont conform to the real requirements
• Cost for corrections are disproportionately high
• Important concepts and decisions are not documented
• Very often this development model is applied altough it is uneconomical

Question 5

Waterfall Model

Answer 5

• We work from top left to bottom right
• If errors are detected we go back to the corresponding activity

Question 6

Waterfall Model - Benefits

Answer 6

• Supports project management
• Supports planning and controlling

Question 7

Waterfall Model - Problems

Answer 7

Assumptions:
- Requirements are known up front before design
- Requirements rarely change
- Users know what they want and rearely need visualization
- The system is not so complex

Question 8

Spiral Model

Answer 8

1. Reaction to waterfall model
2. Core idea: Always react to development risks
3. Repeat the cycle until the project is finished successfully or it fails
   - Identify all the risks
   - Assess all risks to get the most important one
   - Select an approach to eliminate the risk and apply this approach

Question 9

Incremental Development

Answer 9

Basic idea: We dont develop the whole system

Question 10

Incremental Development - Benefits

Answer 10

• Project progress is shown not by documents but by executable systems
• Each increment implements a defined set of requirements
• allows for software to evolve, not be produced in one huge effort
• allows software to improve, by giving enough time to the evolutionary process itself
• forces attention on stability, because only a stable foundation can support multiple additions

Question 11

Iterative Development

Answer 11

• Controlled continuous revision of software aiming at correcting errors early and integrate improvements
• We get things wrong before we get them right
• recognizes the reality of chaning requirements
• promotes early risk mitigation, by breaking down the system into mini-projects and focusing on the riskier elements first
• allows you to plan a litte, design a little, code a little

Question 12

Prototyping - Idea

Answer 12

• It is easier to describe a system relatively to a similar system than to abstractly specify its requirements
• Experiences gained in building a prototype are useful for the final system development

Question 13

Prototyping - Implications

Answer 13

• A prototype hat to be executable / performable
• It only implements some selected attributes of the final system
• It has to be used and assesses by users / clients
• Based on the feedback, it is modified until it fits to what the user wants