XXX copy in a well-written existing definition here
A capability is a reference which combines designation with authority.
Designation is ...
Authority is ...
- Object references in object-oriented programming languages, provided that they have encapsulation and do not have other ways to acquire references (XXX explain or move to page on Object-capabilities)
- capabilities, or "keys", in capability operating systems such as KeyKos, CapROS, or Coyotos
- an Actor address + an facet identifier? (XXX what is this?)
(XXX improve this section)
See What is a Capability, Anyway? for a partisan explanation of what capabilities actually are.
See also Overview: Capability Computation