A string that forms one third of the unique key for the entity being represented. Being the 'id' part of the globally unique key 'type/source/id', this value should identify a specific entity of the given 'type' from the given 'source'.

A string that forms one third of the unique key for the entity being represented. Being the 'source' part of the globally unique key 'type/source/id', this value should be unique the source (like a file name or sql connection) when whence the entity come. This field is only important if enteties of this type can come from different sources.

A string that forms one third of the unique key for the entity being represented. Being the 'type' part of the globally unique key 'type/source/id', this value should be unique for your code and not clash with 'type' strings used in other code modules.