Bondage and discipline, domination and submission, sadism an masochism. Sex isn't necessary to any part of BDSM, it just often comes along with it. There are plenty of ways to practice BDSM without sexual interaction.
Clothing control, masturbation control, daily chores, rituals, food control, bathroom control, tasks...these are all fairly common and none require either of you to lay a finger on each other, or even be in the same building.
The only thing that's necessary for a BDSM relationship is someone giving up control and someone else receiving it. Each individual relationship varies in the activities and boundaries within in the relationship.
Looking for an online relationship/ Seeking a Dom