What's abs got to do with it? The abs are the core, everything ties together in the solar plexus. As the next step in "Yoga Chuck's Physical Routine" series I do ab work three times a week spending about 10 - 15 minutes per session.
In my Yoga practice I do Paripurna Navasana (Full Boat Pose), one of the many poses to work the abs. Most all Yoga poses literally incorporate the abdominal muscles as well as the rest of the body linking it all together working as one. But at the end of my practice, I work the abs again isolating certain abdominal muscles.
I use "Men'sHealth" "The Book Of Muscle" for my ab work. It's the best book I've ever used for working on building strength and muscle. I only do the ab parts of the book now. Currently I get my strength workout from my Yoga and yes it does give you strength. For women it looks like the "Women'sHealth" "The Women'sHealth Big Book Of Exercises" will do the job for you if your looking for extra core work. It has a whole section on core exercises.
Some advanced Yoga poses especially arm balancing poses use a lot of core strength, so besides functioning better in everyday life, you'll be able to work on more advanced poses that require strong abs.
I follow the exercises in the book but double the three week series, they recommend, to six weeks, then I take a week off for recovery. Then start the next group of exercises to isolate the muscles in a different way.
I don't believe doing extensive ab work is a necessity but for me I feel it gives me balance and centering that is part of what brings everything together for me.
Remember this, if you work one side of the body you should work the other. So I do back bends in my Yoga practice. Setu Bandha Sarvangasana (Bridge Pose), Dhanurasana (Bow pose), Urdhva Dhanurasana (Upward Bow, Full Wheel pose) and other poses to incorporate back bending to balance the ab work. Basically if you only work one side of the body it will be out of balance. I believe Alignment and Balance is Health.
Start slow and keep it simple, if you add to much to soon or try complicated ab work you'll lose your motivation and stop.
Healthy & Happy,