I'm writing to expand on catwoman's post, with some examples.
My boundaries are about me. Yours are about you. Boundaries respect other people's autonomy without controlling them.
A healthy boundary is in the form
If you do A, I'll do B - or -
If you don't do A, I'll do B.
IOW, my boundary is about what I will do when faced with certain sitches.
For example,
'If you get home too late to eat dinner with the family, you're on your own for dinner.'
'No screens until you do your homework.'
'If the car store doesn't meet my price, I'm not buying the car.'
'If you violate an SI guideline, you may suffer a consequence you don't like.'
'If my WS doesn't meet my requirements for R, I'll initiate D proceedings.'
The child gets to choose when to do homework. The child or H or W gets to choose their arrival time. The management at the car store is free to meet your price or not. The mods will talk with you about your guideline violation, if they catch it. Your WS is free to meet your requirement or not.
In all these cases, you get to choose your response - which you've already set up in your boundary. Late arrivals have to get their own dinner. No screens until homework is done. Meet your price, or you walk. Post within guidelines or not. Accept your requirements, or you walk.
The person who has to deal with consequences of violating your boundary may believe you're controlling, but that's the violator's problem.
I think one crosses into an attempt to control if one doesn't impose the consequences and instead does some sort of pleading with the violator to honor the boundary.
Oh, you poor thing! I'll make up a dinner plate for you.
I know you love your video games, and I can't bear to see you unhappy, so you can play Madden even though you haven't even started your homework.
I know it's $1,000 more than we agreed to spend, but I'll buy the car anyway.
I'm so triggered that I have to post this, even though it might violate a guideline!
I don't want to D. My WS has to change!
*****
A boundary is often called an ultimatum by people who don't like other people's boundaries.
I'm OK with that. Both boundaries and ultimatums have the same form:
If you do/don't do A, I'll do B.