Component Technology Introduction

Comp Tech Basics

component technology driving forces

extensibility, coupling, complexity

coupling 1

a depends on b, good

coupling 2

a depends on b doing its job in a particular way, bad

coupling 3

a depends on b having a particular bug, very bad

coupling 4

a depends on b but no one knows, very bad

complexity 1

system becomes too complicated to understand

complexity 2

the people who did understand it leave, retire, die

complexity 3

the system can’t be changed and becomes fragile

complexity 4

the eventual failure is catastrophic

platform requirement 1

common stable interface within which the actual functions may change

platform requirement 2

keep macro-level things the same but evolve the micro-level things

subsitutability

replace a component with another compatible one without any noticeable functional change

subsitutability pro 1

makes change easier due to known boundaries e.g., changing a lightbulb without affecting the lamp stand, switch etc

subsitutability pro 2

allows for piecewise upgrades e.g., change all lightbulbs in a house to low-energy without changing the wiring

why does subsitutability work 1

standard functions

why does subsitutability work 2

standard interfaces

software components definition (szyperski)

binary units of independent production, acquisition and deployment that interact to form functioning systems

unit of composition

we compose components and don’t look inside them

interfaces

only access the services of the component through well-known operations

explicit dependencies

component makes known the interfaces, services and components it requires and only requires these to function properly