Software Process Simulation

Question 1

Reasons for simulation

Answer 1

• Human abilities are unknowningly weak in some areas.
• Software development appears to be a complex system
• Software project managers are inevitably trained and assessed ‘on the job’
• The cost of simulation has plummeted in recent years
• Process improvement is recognized as a beneficial approach
• Other industries have reported very successful applications of management simulation
• Software projects are like many other businesses
• Good simulations can lead to good process automation

Question 2

Generation of process alternatives

Answer 2

Input Parameters

Design

Coding

Test

Output Parameters

Question 3

What is a system?

Answer 3

A collection of elements that operate together for a common purpose. It appears as a self-contained unit with a defined structure.

Question 4

What is a model?

Answer 4

An idealized, simplified prepresentation of a real object, system, or other subset of reality, but still similar with respect to certain aspects. it supports the goal to better study certain properties of the actual subject.

Question 5

What is a simulation?

Answer 5

Simulation of a system means to conduct experiments with a model, representing the real system also with respect to its dynamic behavior.

The simulation model can be manipulated in a way that often would be impossible, dangerous, too expensive, or too time consuming with the real system.

Question 6

Simulation Modles

Answer 6

Computerized model that:

• Represents an abstraction of a (complex and) dynamic system
• Is represented and can be manipulated by a computer

Complexity may appear in form of:

• System uncertain and stochastic influences
• Dynamic (time dependent) system bejavior
• Feedback mechanisms

Question 7

Simulating software processes helps to…

Answer 7

• Learn and improve
• Understand and train
• Forecast and plan
• Guide and control

Question 8

Advantges of Simulation and Modeling

Answer 8

• Faster and less expensive compared to experiments with real systems (e.g. pilot projects)
• Focuses with respect to abstraction level and viewpoint
• Repeatable with change or hypothetical starting conditions and external influences

Question 9

Disadvantages of Simulation and Modeling

Answer 9

• The validity of simulation results is difficult to judge (dependent on model validity, correct starting conditions, occurrence of external influences)

Question 10

Limitations of Simulation and Modeling

Answer 10

• You can get dazzled by the precision of the numbers
• The illusion of control may be greater than the reality
• Noise in the system may suggest patterns that do not really exist
• Accurately quantifying non-numeric information can be difficult

Question 11

What is Model Verification

Answer 11

• Checks the internal correctness (appropriateness) of the model
• Question: Has the model been constructed right?
• Requires expert knowledge about the modeling technique (role: modeling expert)

Question 12

What is Model Validation?

Answer 12

• Checks the external correctness (appropriateness) of the model
• Question: Has the right model been constructed?
• Requires expert knowledge about the real system (role: system expert)

Question 13

What is Model Scope?

Answer 13

• A phase or portion of th elife cycle (e.g. design phase, code inspection)
• A development project
• Multiple, concurrent projects (e.g. across a department or division)
• Product evolution
• Organizational strategy development
• Each of tehse categories can be subdivided according to
  
  • Time span (short, medium, long)
  • Breadth (less than one product/project team, one product/project team, multiple products/projects teams)

Question 14

Continuous Simulation

Answer 14

• Ex. Water flow: If the water flow is treated as an aggregation, the flow can eb described a (time-) continuous way, i.e., by differential equations.
• A continuous simulation model represents a system for which the state variables change continuously over time.

Question 15

Discrete Simulation

Answer 15

• Ex. Water flow: Is discrete if the characteristics and movements of individual molecules are important.
• A discrete simulation model is a model of a system which is represented by state variables that change instantaneously at certain points in time, i.e. when certain events.

Question 16

Continuous Models Advantages

Answer 16

• Capture the stability or instability of feedback loops
• Impact factors like experience, fatigue schedule pressure, fatigure are easier to model.

Question 17

Continuous Model Disadvantages

Answer 17

• Sequential activities in the process are only possible to model with additional mechanisms
• All items (e.g. modules, developers) are equal
• Distributions over properties of items are difficult to model.

Question 18

Discrete Event Model Advantages

Answer 18

• Entities can contain unique values for attributes
• Usage of distributions for code complexity, programmer capability, size, # of defects, …

Question 19

Discrete Event Model Disadvantages

Answer 19

• Continuous variables are only updated at the event times
• Computation errors may lead to instability in feedback loops
• Parallel activities are difficult to model.

Question 20

System Dynamics

Answer 20

• The basic concept of System Dynamics is Systems Thinking (systems oriented / holistic / network oriented thinking)
• Systems Thinking is characterized by
  
  • Thinking in cause-effect mechanisms instead of static correlations (white-box vs. black-box)
  • Considering multi-casual conjunctions (no mono-casual thinking)
  • Taking feedback into account
  • Considering the dynamic (not only the static) complexity
  • Considering reality to be a closed system.
• A graphic modeling language makes modeling easy
• Mature tool support is available at relative low costs

Question 21

Simulations to support multi-criteria decision-making

Answer 21

In the tension between cost, time and quality; simulations help in mastering processes and process improvement.