The Solais system was an independent star system.
In 2365, the Federation starship USS Enterprise-D ferried a mediator to Solais V. He was there to negotiate a peace to a centuries long planetary conflict. (TNG: "Loud As A Whisper")
In 2371, the SS Xhosa ferried cargo to Solais V. (DS9: "The Adversary")
According to the script for "Loud As A Whisper", the name of this system was pronounced "So-LAY-is."