I always like to complement the product vision and product strategy with a set of product principles.
Where the product vision describes the future you want to create, and the product strategy describes your path to achieving that vision, the product principles speak to the nature of the products you want to create.
Product principles are not a list of features, and they are not tied to any one product release. The principles are aligned with the product vision for an entire product line.
A good set of principles may inspire some product features, but it's more about what the company and product teams believe is important.
As an example, early on at eBay we found we needed a product principle that spoke to the relationship between buyers and sellers. Most of the revenue came from sellers, so we had a strong incentive to find ways to please sellers, but we soon realized that the real reason sellers loved us was because we provided them with buyers. This realization led to a critical principle that stated, “In cases where the needs of the buyers and the sellers conflict, we will prioritize the needs of the buyer, because that's actually the most important thing we can do for sellers.”
Where the product vision describes the future you want to create, and the product strategy describes your path to achieving that vision, the product principles speak to the nature of the products you want to create.
These are what principles are all about. You can imagine how this type of principle would help with designing and building a marketplace and how many issues could be resolved by simply keeping it in mind.
Whether you choose to go public with your principles depends on your purpose. In many cases, the principles are simply a tool for the product teams. But, in other cases, the principles serve as a clear statement of what you believe—intended for your users, customers, partners, suppliers, investors, and your employees.