I first did this analysis at Nordstrom back in 2003. One of my analysts and I created linkages between Merchandise Categories.
The hypothesis was simple ... do one or two key Merchandise Categories fuel growth in other Merchandise Categories? Are there Linkages between Merchandise Categories that help us understand the role each category plays in the merchandising ecosystem?
The answer was a clear YES!!
Way back in the day at Nordstrom, Cosmetics and Womens Shoes attracted prospects into the store. If the customer bought from one of those two categories, the customer then moved deeper into the ecosystem, buying Accessories or Womens Apparel. In other words, Accessories and Womens Apparel were "linked" to Cosmetics and Womens Shoes.
Why does this matter?
Well, guess what happened to Womens Apparel if we messed up Cosmetics? Because Womens Apparel was "linked" to Cosmetics, Cosmetics played a "double role" ... it had to perform well to thrive, but it also had to feed customers to Womens Apparel (and Accessories).
Once you understand what your "linkages" are, you know how to merchandise landing pages, your home page, your email campaigns, and for those of you with print you know how to merchandise your catalog.