How do you define BDSM?

I tie up my wife, we have floggers and steel collars chains and shackles. Spankings are very common in our house when she deserves them. We have a 24/7 D/s lifestyle. If I am in the mood she needs to ask my permission to do anything including going to the bathroom and having permission to sleep in our bed. I have a very naturally submissive wife so this works for us. It can be very difficult to find a partner who is the right match of submissive to your dominance and vice versa. I have certain expectations of her and if they are not met, she is punished.
BDSM is also a very large part of our sex life. She is often tied up and is never in control in any sexual situation. We have been together for many years and married for almost 5 years and are 100% faithful to eachother. This is a very natural part of our relationship and we have fun with it.