Nomad:

As I see it, most of your questions center around two points: metadata and design decisions. When you design an application, you'll have to decide what state information you want to keep about each object. You'll also have some information *about* the state information (the metadata). In some applications, you'll keep track of the metadata and in others, you won't. These are the choices you'll make as a designer.

Many of the specific questions you're asking are for clarifications of definitions--however the definitions are application-dependent as well. For one application, "modified" may mean a change to the values of a node, while for another application "modified" may mean a change to the data and/or metadata.

You should be able to resolve many of those questions by clarifying/negotiating the requirements with your users. For example, it may mean that you'll have several "modified" values, one for permissions changes, one for value changes, one for ....etc.

...roboticus