### Instruction:

Extract the cause and effect entities from the following sentence:
While the class BrandOwnerOfTradeItem is optional, the party identification for the brand owner is required when a brand owner is present

### Assistant:

KEYWORD: when
VARIABLE: a brand owner
CONDITION: is present
CAUSE_1: the class BrandOwnerOfTradeItem is optional
EFFECT_1: the party identification for the brand owner is required
CAUSE_2: a brand owner is present

