Return canonical entity
When defining "phrase list features" allow for grouping of possible values as synonyms with a canonical value e.g.
"document", "documents", "file" and "files" when picked up by the LUIS engine will be returned as an entity "document" (the nominated canonical value).
Handling on the LUIS server means I don't have to duplicate and maintain lists of synonyms across the server and all my clients
This is how entities currently work in LUIS. For more information, please see: https://docs.microsoft.com/en-us/azure/cognitive-services/luis/luis-concept-entity-types.