is there a science to good chicken salad?

Baking is a science. Chicken salad is not.
Let me explain. I don't find good chicken salad to be dictated by a set of weights and measures. There is room for improvisation and customization. That said, there are still some general rules that must be followed if you want to please the chicken salad tasters at my house:
-Use only oven roasted, bone-in chicken OR poached chicken. Anything else tends to be dry. My favorite version, pictured above, is made with Rosemary Poached Chicken... which simply requires a few chicken breasts, a little bit of water and white wine and a sprig of fresh rosemary. Poach until done throughout.
-Once cooked, breasts should be pulled, not cubed. (This is truly a matter of personal preference, and well, that's our preference.)
-Chicken salad should contain halved grapes and pecans. This is my husband's requirement. It's a throwback from the chicken salad his grandmother made when he was a child.
-Chicken salad must contain at least a touch of mustard. Dijon is divine, but yellow will do. A lot of novice chicken salad chefs skip this step. I think that's a shame.
-High quality mayonnaise is a must. "Which" mayo is the highest quality is a debate that I'm sure has divided bridge circles throughout small southern towns for miles around. I think I'll leave any more personal mayo preference musings alone for fear of offending those who don't agree with me. Mayo is serious business.
The rest of the recipe is really up to the chef. You can opt for roasted breasts and then add fresh thyme, rather than using the rosemary poached. Or maybe you prefer to use celery, rather than sweet pickle and add a little dill. There are lots of variations, all worth trying. As I said, this is not an exact science. But there's definitely a recipe for success.
Question: what makes your chicken salad special?