map

map FooCounter[deviceId: ?]=>{count: ?} as counter {
    check counter.count > 0
}

map executes a fact query, and for each fact found, defines the given name as a struct containing the fact’s fields. This can result in zero or more iterations. Just like in query, the value side of the fact can be omitted if all its fields are bound.

You can think of this kind of like a for loop over all possible matching facts. The name given after as is scoped to the block.

map can be nested.

map Devices[deviceId:?] as device {
   map Keys[deviceId: device, id: ?] as key {
       check owner.valid
   }
}

Like query and related functions, fact values or the entire value part of the fact literal can be omitted. And likewise, bind values must follow the positioning rules.