Commander Parker was a member of Starfleet in the 2370s.

He was the second-in-command of the unit that was assigned to protect the Dominion communication array on AR-558 after the Federation Alliance captured the Chin'toka system in late 2374. He was later killed, and command of the depleted unit passed to Lieutenant Nadia Larkin. (DS9: "The Siege of AR-558")

This character was only mentioned in dialogue.
According to the Star Trek: Deep Space Nine Companion, Parker's name was an homage to Fess Parker, who played Sergeant Pike in the movie Hell Is for Heroes.
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