Fifth law?

I found that Krug has already tried to lay claim to 'laws of usability'. I don't think his really work as general design rules though, they are very much tied to design of Web sites.

One point though, the exposition should be of cause to effect. For example: The user will be frustrated if they cannot find the information they need for their task. Same essential point, but an is rather than an ought.

While thinking about the point I thought of a fifth law: When tasks that the user considers atomic are presented require multiple interactions with independent systems inconsistency will result.

The reason I got thinking about this was the current problem of administering a service such as email that requires both local service configuration and a DNS configuration and quite possibly firewall configuration as well. From the network architecture point of view these are 'obviously' independent systems. From the network administrator's point of view they are all parts of one single task.

There is a heavy bias in network administration towards an imperative mode of configuration rather than the declarative. Instead of announcing to the infrastructure 'this machine is to be a mail server' we have to know what being a mail server is and configure the necessary support services and connectivity piecemeal.