In a certain code language, '-' represents '+', '+' represents 'x', 'x' represents '÷' and '÷' represents '-'. Find out the answer to the following question.
Shubham's mother is the sister-in-law of Shashi and Shashi is the only daughter of Parmeshwar. Ravi is Shubham's brother. How is Shashi related to Ravi?