'adiwg-mdCodes' is a Rubygem for delivering managed lists to an application. mdCodes has a set of methods to access a codelist and return the list in either a JSON object or Ruby hash. Each 'static' codelists is stored in a single YAML file with a code, code name, and definition for each codelist item.

The codelists were developed to support creation of ISO Geospatial Metadata standards and were extended by the Alaska Data Integration working group (ADIwg) to support mdJson.