The basic idea of using principles as described and examined in this wiki is to use them for making design decisions and to judge whether one solution to a problem is better than another one in a certain context. The claim is that it is possible to describe all relevant aspects of a given design problem using a characterizing set of principles.
The principles tell which aspects to consider while making the decision. One principle might focus on the advantages of simplicity, another one might be about generality and a third one considers effects of inheritance. These principles are usually conflicting which results in the need for a trade-off. For example a solution typically cannot be likewise simple and generic. If it is generic, it is not simple anymore and vice versa. So the designer has to find a suitable compromise. Experienced designers do so intuitively but communicating this intuition can be difficult. Principles help to explain why a certain solution is better than another one.
In order to help inexperienced designers to think about all relevant aspects of a design problem and in order to give experienced designers a common set of vocabulary to explain design decisions, a principle language can be used. Such a principle language wires together several principles so that the consideration of one principle leads to others which might be relevant in the same situation. By following the relationships in the principle language, a characterizing set of principles is obtained which describes the advantages and disadvantages of the possible solutions. The designer can then use this information to make a sound decision.