### Instruction:

Extract the cause and effect entities from the following sentence:
The SIP URL of a given stream could, if not previously known, be registered under a DNS name using a DNS TXT record

### Assistant:

KEYWORD: if
NEGATION: not
CONDITION: be registered under a DNS name using a DNS TXT record
CAUSE_1: not previously known
VARIABLE: The SIP URL of a given stream
EFFECT_1: be registered under a DNS name using a DNS TXT record

