• The minor version changes whenever a dictionary adds new fields, but does not modify existing fields. This means the consumer can still use the previous dictionary with its data (though the consumer is unable to decode any new fields). Also, if the consumer has multiple dictionaries with the same major version available, it can use the minor version information to determine which is the latest (and therefore will be able to decode all fields regardless of the data’s source).
• The major version changes if the dictionary changes in a way that is not compatible with previous versions (such as changing an existing field). This means that data encoded using a dictionary with one major version cannot be decoded using a dictionary with a different major version. If a consumer learns that its provider has changed to a dictionary with a different major version, it must retrieve the new dictionary before again decoding data.