CSC/ECE 517 Fall 2009/wiki3 5 SD

Dependency inversion principle

Dependency inversion principle states that:

1. High-level modules should not depend on low-level modules. Both should depend on abstractions.

Abstractions should not depend upon details. Details should depend upon abstractions.

Introduction

In conventional application architecture, lower-level components are designed to be consumed by higher-level components which enable increasingly complex systems to be built. In this composition, higher-level components depend directly upon lower-level components to achieve some task. This dependency upon lower-level components makes applications rigid, fragile and immobile.