High Level Design Principles

2020, Aug 10    

These are some of the guiding high-level principles which are important to keep in mind while desiging software component/system

Enforce Loose Coupling

• Two classes, components or modules are coupled when at least one of them uses the other. the less these items knows about each other, the losser they are coupled.
• A component that is only loosely coupled to its environment can be more easily changed or replaced than a strongly component.

Adopt High Cohesion

• Cohesion is the degree to which elements of a whole belong together.
• Methods and properties in a single class and classes of a component should have high cohesion.
• High Cohesion in classes and components results in simpler, more easily understandabe code structure and design

Enable design which will help changed to local as much as possible

• When a software system has to be maintained, extended and changed for a long time, keeping changes local reduces involved costs and risks.
• Keeping change local means that there are boundaries in the design which changes should not cross.
• Design by contract and perfer Dependency Inversion Principle

It should be easy to remove

• We normally build software by adding, extending or changing features.
• Removing elements is important so that overall design can be kept as simple as possible.
• When a block (Method, Class, Component, Module) gets too complicated, it has to be removed and replaced with one or more simpler granular blocks

Design Mind-Sized Components

• Break your system down into components that are of a size you can grasp within your mind so that you can predict consequences of changes easily. (dependencies, control flow, ..)