Standard Development Lifecycle

1960s – first significant model developed – Standard Development Life Cycle (SDLC), also known as waterfall method. Splits software development process into stages: Requirements Analysis Design Build Test Implementation Maintenance Model has high level of abstraction – seven stages. No models have lower abstraction guiding development process. Has Systems Thinking approach – Maintenance loops back into Requirements – software development […]

Development Models Introduction

Will be discussing models used in Systems Engineering field with emphasis on software development process and role of models in Information Systems design. Specifically look at role models play in development of software-based systems. These models used across other engineering disciplines, original mnemonic SDLC stood for Standard Development Life Cycle. Software produced to support systems – different descriptions include; data […]


Important concept and practise. Repeat analysis process several times to identify/enhance facts, data and understanding. Iteration, along with different views, helps produce robust analysis.

Decision Trees

Identifies options available and key choices. Analysis of complex decisions with significant uncertainty can be confusing because: the consequence that will result from selecting any specified decision alternative cannot be predicted with certainty. there are often large number of different factors that must be taken into account may be useful to consider possibility of reducing uncertainty in the decision by […]

Cause and Effect Diagram

Cause and Effect diagrams sometimes called fishbone diagrams or Ishikawa (name of the developer). Models casual relationships that occur. Identifies what is causing what effect. Will identify multiple causes if they exist – critical for understanding complex situation. Will also identify feedback loops. Diagram focuses on causes rather than effect. Start with definition of problem and then ask why is […]

Further Model Types and their uses

Rich Pictures Often first stage in design process Free format diagram to capture system Identifies politics, processes, emotions Theme places in middle, link words placed around it Systems Dynamics Show states and rates for given situation Example: human population and rate of increase/decrease Other states can be modelled against human population such as food consumption, food production, water consumption Allows […]

A brief summary of Model Considerations

Number of elements to consider when building models: Define model purpose when designing model. Model should be verified and validated. Designed by humans from specific perspective, may be flawed. Model only gives partial view of situation/system. Number of models required to gain full understanding of situation/system providing different views. Abstraction level required is key decision.

Other Classification Systems

In addition to static and dynamic, models can also be defined as quantitative and qualitative. Quantitative models similar to numeric models quantify situation¬†with facts and data Qualitative models shows structure of elements/components Other model classifications are hard and soft models. Hard models are like quantitative models and are based on facts and data. Soft models are like qualitative models and […]