The items in a collection in this specification are unordered and may contain duplicates.

An ignorable policy assertion is an assertion that may be ignored for purposes of determining the compatibility of alternatives in policy intersection in a lax mode (as defined in 4.5 Policy Intersection).

A nested policy expression is a policy expression that is an Element Information Item in the children property of a policy assertion.

A policy is a potentially empty collection of policy alternatives.

A policy alternative is a potentially empty collection of policy assertions.

A policy assertion represents a requirement, a capability, or other property of a behavior.

A policy assertion parameter qualifies the behavior indicated by a policy assertion.

A policy assertion type represents a class of policy assertions and implies a schema for the assertion and assertion-specific semantics.

A policy attachment is a mechanism for associating policy with one or more policy scopes.

A policy expression is an XML Infoset representation of a policy, either in a normal form or in an equivalent compact form.

A policy scope is a collection of policy subjects to which a policy may apply.

A policy subject is an entity (e.g., an endpoint, message, resource, operation) with which a policy can be associated.