Flow mappings in YAML represent the unordered collection of key value pairs. They are also called as mapping node. Note that keys should be maintained unique. If there is a duplication of keys in flow mapping structure, it will generate an error. The key order is generated in serialization tree.
An example of flow mapping structure is shown below −
%YAML 1.1 paper: uuid: 8a8cbf60-e067-11e3-8b68-0800200c9a66 name: On formally undecidable propositions of Principia Mathematica and related systems I. author: Kurt Gödel. tags: - tag: uuid: 98fb0d90-e067-11e3-8b68-0800200c9a66 name: Mathematics - tag: uuid: 3f25f680-e068-11e3-8b68-0800200c9a66 name: Logic
The output of mapped sequence (unordered list) in JSON format is as shown below −
{ "paper": { "uuid": "8a8cbf60-e067-11e3-8b68-0800200c9a66", "name": "On formally undecidable propositions of Principia Mathematica and related systems I.", "author": "Kurt Gödel." }, "tags": [ { "tag": { "uuid": "98fb0d90-e067-11e3-8b68-0800200c9a66", "name": "Mathematics" } }, { "tag": { "uuid": "3f25f680-e068-11e3-8b68-0800200c9a66", "name": "Logic" } } ] }
If you observe this output as shown above, it is observed that the key names are maintained unique in YAML mapping structure.