minecraft-bedrock-json-schemas/source/general/item/identifier.json

{
  "$id": "blockception.minecraft.item.identifier.1.8.0",
  "type": "string",
  "title": "Item Identifier 1.8.0",
  "description": "The minecraft item identifier",
  "pattern": "^[0-9a-zA-Z:_\\-\\.]+$"
}