Why do we model?

• A model is a simplification of reality. We model because we cannot comprehend the complexity of a system in its entirety.
• We model to visualize, specify, construct, and document the structure and behavior of a system's architecture.
• A model is a complete description of a system from a particular perspective.

Principles of Modeling

• The choice of what models to create has a profound influence on how a problem is attacked and how a solution is shaped.
• Every model maybe expressed at different levels of precision.
• The best models are connected to reality.
• No single model is sufficient. Every non-trivial system is best approached through a small set of nearly independent models.

Basic Principles of Object Orientation

• Abstraction: the most important or essential aspects of something while ignoring the less important details. Abstraction is dependent on perspective - what is important in one context may not be in another. We model our problem domain using abstractions.
• Encapsulation: physical localization of features into a single blackbox abstraction that hides their implementation behind a public interface. "Information hiding".
• Hierarchy: organization of abstractions according to some order (e.g. complexity, responsibility, etc.).
• Polymorphism: substitute variables or objects or one type with variables or objects of another type. Polymorphism gives us the ability to switch components without loss of functionality.