w动态实例化-轻量级，组件间依赖程度、专一性-复用性、灵活性。
https://www.codeigniter.com/userguide3/overview/goals.html
http://codeigniter.org.cn/user_guide/overview/goals.html
Design and Architectural Goals
Our goal for CodeIgniter is maximum performance, capability, and flexibility in the smallest, lightest possible package.
To meet this goal we are committed to benchmarking, re-factoring, and simplifying at every step of the development process, rejecting anything that doesn’t further the stated objective.
From a technical and architectural standpoint, CodeIgniter was created with the following objectives:
- Dynamic Instantiation. In CodeIgniter, components are loaded and routines executed only when requested, rather than globally. No assumptions are made by the system regarding what may be needed beyond the minimal core resources, so the system is very light-weight by default. The events, as triggered by the HTTP request, and the controllers and views you design will determine what is invoked.
- Loose Coupling. Coupling is the degree to which components of a system rely on each other. The less components depend on each other the more reusable and flexible the system becomes. Our goal was a very loosely coupled system.
- Component Singularity. Singularity is the degree to which components have a narrowly focused purpose. In CodeIgniter, each class and its functions are highly autonomous in order to allow maximum usefulness.
CodeIgniter is a dynamically instantiated, loosely coupled system with high component singularity. It strives for simplicity, flexibility, and high performance in a small footprint package.
设计与架构目标
CodeIgniter 的目标是在最小化，最轻量级的开发包中得到最大的执行效率、功能和灵活性。
为了达到这个目标，我们在开发过程的每一步都致力于基准测试、重构和简化工作， 拒绝加入任何对实现目标没有帮助的东西。
从技术和架构角度看，CodeIgniter 按照下列目标创建：
- 动态实例化。 在 CodeIgniter 中，组件的导入和函数的执行都是在被请求的时候 才执行，而不是全局的。除核心资源外，系统不需要任何其他资源，因此系统默认是 非常轻量级的。HTTP 请求所触发的事件以及你设计的控制器和视图将决定哪些资源是 需要加载的。
- 松耦合。 耦合是指一个系统中组件之间的依赖程度。组件之间的依赖程度越低， 系统的重用性和灵活性就越好。我们的目标就是打造一个松耦合的系统。
- 组件专一性 专一性指的是组件对某个目标的专注程度。在 CodeIgniter 中， 每一个类和方法都是高度独立的，从而可以最大程度的被复用。
CodeIgniter 是一个动态实例化，高度组件专一性的松耦合系统。它在小巧的基础上力求做到 简单、灵活和高性能。