This page is a really good one, explains quite some things in an interesting way. Here are some of the principles that are applicable in a wider context in general:
- If a system is to serve the creative spirit, it must be entirely comprehensible to a single individual.
- A system should be built with a minimum set of unchangeable parts; those parts should be as general as possible; and all parts of the system should be held in a uniform framework.
- [The purpose of a language is] To provide a framework for communication.
- The design of a language for using computers must deal with internal models, external media, and the interaction between these in both the human and the computer.
- A computer language should support the concept of “object” and provide a uniform means for referring to the objects in its universe.
- To be truly “object-oriented”, a computer system must provide automatic storage management. [c++ lacks this]
- Computing should be viewed as an intrinsic capability of objects that can be uniformly invoked by sending messages.
- A language should be designed around a powerful metaphor that can be uniformly applied in all areas.
- No component in a complex system should depend on the internal details of any other component.
- A language must provide a means for classifying similar objects, and for adding new classes of objects on equal footing with the kernel classes of the system.
- A program should specify only the behavior of objects, not their representation.
- Each independent component in a system would appear in only one place.
- When a system is well factored, great leverage is available to users and implementers alike.
- Every component accessible to the user should be able to present itself in a meaningful way for observation and manipulation.
Well worth going through it once.