Security can be handled at the machine, domain, or sharepoint level.

Unfortunately, no. At this point, we don't offer domain names for SharePoint sites. But very soon
we will be making this available for all our SharePoint site customers. Please keep checking this
page for further update on this. Meanwhile, we suggest you go ahead and set up your site and
create content for it.

Multiple hosts plus domain names mapped to a single IP address.

A scope over which the same security mechanism is used to enforce a security policy. Multiple security policy domains can exist within a single technology domain.

A scope over which security policies are defined and enforced by a security administrator. A security policy domain has a collection of users (or principals), uses a well-defined authentication protocol or protocols for authenticating users (or principals), and may have groups to simplify setting of security policies.

The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL

The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.