Passing value/trust/juice to other pages - schema

I think you should read this example to understand the usage of relation nofollow in structuring your page and link architecture.

First, let me tell you that there are lots of factors to be take in consideration, that I will give you is just a basic, a way to start understanding. It is not an accurate schema and it will never be ( since things change really fast when we are talking about Search Engine Algorithms ).

We have the example "shopping cart". We have build a site or a landing page and we need to rank well for "shopping cart". We set the title of the new page like this

UK Shopping cart - ecommerce script London
after we will change it in just

UK shopping cart
now let us see why we made that change in order to get better changes of ranking well

Code:
UK Shopping cart - ecommerce script London  = 6 strings
calculatate a 100% / 6 strings = 16.6 % relevance for each string
since we have a combined keyphrase, lets calculate it for "shopping cart"

UK Shopping cart - ecommerce script London = 5 strings
100% / 5 = 20% for each string
now we take example number two for a page title
UK Shopping cart = 2 strings ( because of the combined keys )

so each takes = 50%
( again the calculus is not that exact here, since the combined phrases shopping + cart at a single string calc would have been 33% + 33% = 66% > 50% relevance, but as I said, the example is purely for understanding how things work )

So, checking the above, we notice that we get better relevance for a short title ( 50 to 66% ) than a longer one ( 20 to 36% )

So the site/landing pages has already better changes to rank well. Now we go on to the next factor : internal linking and setting the anchors correct. After that is links from external sources ( the backlinks ). After that is the keyphrases density -> simple and combined. And so on.

It is important to see where you want to go, to know the target so that you can create some kind of reports, knowing where you are close or when you need to improve something to have better chances of ranking