In the first paragraph of section 7.4.1 of the GDDI version 1.0 specification, where it says "separate repository linked from this specification or OMG website (e.g., wiki or GitHub repository)" add the following link to the official GitHub location of the GDDI Data Dictionaries:
https://github.com/ObjectManagementGroup/GDDI

The GDDI standard supports backward compatibility where an endpoint that implements a newer minor-version Type Block, containing newly added TLV(s), can receive GDDI messages with an older minor-version Type Block that does not contain those newly added TLV(s). In this case the receiving endpoint needs to assign those value(s) to a default. Currently, the convention is to define a default value for each TLV in the 'description' field within the GDDI Dictionaries via the following format: "(Default: <VALUE>)". This requires the receiving GDDI endpoint to parse-out each default value instead of having its own field. Consider adding a dedicated field for this Default Value to explicitly define it.