First you have to buy a primer specifically designed for wood floors. Tell the paint store professional what you intend to do and decide on what paint and color you want to use. Latex paint needs a latex primer, but an alkyd primer can be used for alkyd, polyurethane and latex.
Now that you have chosen your paint color decide on the finish. Example if you're looking for a satin finish, you should use latex floor paint. If you want a semi-gloss or gloss finish, use alkyd, polyurethane or latex floor paint.
What exactly are you painting? I didn't see any mention of floors in your original post.
Under normal circumstances you could use a latex primer over maple (like 1-2-3) - however if there are a lot of knots I feel an oil based primer would be better - Bin would even be better still for knots but I'm not sure exactly what you are doing.
To clarify the previous post - you CAN use an oil based primer under a latex floor paint - in fact, if you read the back of most latex floor paints, they claim to be self priming but tell you not to apply directly to bare wood. The reason for this is that the latex paint can/will cause the wood grain to rise. Priming with an oil based primer will elminiate the wood grain rise.