SE-Software Process Model

What is a software process model?

• A software process
  • is a set of activities whose goal is the development or evolution (演变) of software
• Software process model
  • a simplified representation of a software process from a specific perspective.

What process models have we learnt in this semester?

Waterfall model

• A process that flows in one - direction, involving analysis, design, coding, testing, and maintenance in sequence.

• Advantage:

  • Straightforward and Disciplined

• Disadvantage:

  • Users cannot describe their requirements very clearly at the beginning
  • Hard to follow
  • The projects developed with this process are often delayed

Incremental process model

• Allows doing the most important features first and adding the rest later, with a loop in the process for adding more requirements.

• Clients do NOT need to specify the requirements for the whole system at the beginning

• Clients can specify the most important parts to finish first

• It requires more testing each time a new increment is added compared to the waterfall model.

• Advantage:

  • The risk that the whole system fails is lower (compared to the waterfall model)
  • Shorten the delivery time

• Disadvantage:

  • The system structure is loose
  • Hard to define the increments

Prototyping model

• A quick design -> the construction of a prototype

• Identify software requirements

• Paper work Prototype: A non-computerized form of prototype, likely involving physical or hand-drawn representations to give an initial idea of the system.

• Computer programs Prototype: A prototype in the form of a computer program, which can be evolved into the final system.

  • This allows developers to have a quick design and for users to get an initial look at the system.

• Advantages:

  • Users can have an initial look of the system
  • Developers have a quick design
  • The prototype can be evolved to a system

• Disadvantages:

  • Rush to get it work
  • Hard to ensure the quality and to maintain

Spiral model

• proposed by Barry Boehm

• An evolutionary（演变） (iterative) software process model

• Combine both waterfall model and prototyping model

• Many variants are available

• Advantages:

  • Developers can using prototyping in each evolutionary level
  • Reduce the risk

• Disadvantage:

  • Continual risk analysis
  • Document maintenance

Rational Unified Process

• A process includes many cycles

• One cycle includes four phases

  • Inception
  • Elaboration
  • Construction
  • Transitions

• One phase includes several iterations

  • Workflows are in one iteration

• Advantages:

  • Combine several process models
    • Support prototyping and incremental delivery
  • Illustrate good practices in specification and design

• Disadvantage:

  • Not suitable for embedded software development