+h4(#filterexpression). Filtering using boolean expressions
+
+In addition to the three-element array form described above, a string containing a boolean expression is also accepted. The following restrictions apply:
+* The expression must contain exactly one operator.
+* The operator must be @=@, @<@, @<=@, @>@, or @>=@.
+* There must be exactly one pair of parentheses, surrounding the entire expression.
+* Each operand must be the name of a numeric attribute like @replication_desired@ (literal values like @3@ and non-numeric attributes like @uuid@ are not accepted).
+* The expression must not contain whitespace other than an ASCII space (newline and tab characters are not accepted).
+
+Examples:
+* @(replication_desired > replication_confirmed)@
+* @(replication_desired = replication_confirmed)@
+
+Both types of filter (boolean expressions and @[attribute, operator, operand]@ filters) can be combined in the same API call. Example:
+* @{"filters": ["(replication_desired > replication_confirmed)", ["replication_desired", "<", 2]]}@
+
+h4. Federated listing
+
+Federated listing forwards a request to multiple clusters and combines the results. Currently only a very restricted form of the "list" method is supported.
+
+To query multiple clusters, the list request must:
+
+* Have filters only matching @[["uuid", "in", [...]]@ or @["uuid", "=", "..."]@
+* Specify @count=none@
+* Not specify @limit@, @offset@ or @order@
+* Not request more items than the maximum response size
+
+This form may be used to request a specific list of objects by uuid which are owned by multiple clusters.
+