While in many cases the domain structure will reflect your project structure just because it is natural for data like axes, classifications etc. to change with projects you should carefully plan the structure of your domains.

Changing the parent of a domain and therefore restructuring your domain tree might not be possible in all cases as soon as features, and sensors are assigned to that domain.

Figure1: Example of a domain structure with 2 features

If your Application Server only manages a small amount of data it might be sufficient to assign all features, sensors and other data to the root domain. However if you plan to manage more data with the Application Server a well thought out domain structure is crucial. Thinking of domains as your projects and sub-projects might be helpful when planning the domain structure, however be aware that the Application Server also uses domains to define the availability of data like classifications, axes etc.