List of Software Architecture Laws

There are several universally accepted software architecture laws. These have the characteristic that if you heed their principles, your software will be of better quality and will last longer. These are the ones I am aware of:

Law of Demeter
aka principle of least knowledge, aka only talk to your immediate friends, aka low coupling and high cohesion.

Separation of Concerns
The notion that it is better to allow the code (and the developer) to concentrate on one concern at a time. This is the mother of many other principles, for example layering, or splitting software along logical lines.

Conway's Law
Any piece of software reflects the organizational structure that produced it. The cause is more sociological than technical. The antidote is better communication, or smaller teams.

Shalloway's Law
aka DRY. "When N things need to change and N>1, Shalloway will find at most N-1 of these things". I like Shalloway's version, because it manages to capture the essence of DRY, with the added subtlety that it is ok to duplicate stuff, as long as you don't have to manually change it.