Rihanna & Chris Martin -- Dinner ... Date?

Rihanna and Chris Martin dined at Giorgio Baldi in Santa Monica on Sunday night, leaving us to wonder ... was this or was this not a date?

DATE: They are both single, dinner spot was RiRi's favorite place, they left separate via separate exits to avoid being spotted.

NOT A DATE: The two have collaborated before ("Princess of China"), paps know RiRi goes there a lot (so unless they were sending a message, they just didn't care about being seen).

So we've presented the evidence, now we ask you ...