What's the difference between attribute based access control and activity based access control within cloud authorization context?
Attribute-based access control is an access control (or authorization) model defined by NIST and which promotes the use of attributes to define access control policies. It is an evolution from the role-based access control (RBAC) model which is prevalent today.
Example:
xacml implements ABAC.
You can read more on abac at the NIST website.
Activity-based access control is a term seldom used and seems to be an earlier version of attribute-based access control.