composing multiple bounded contexts in a single user interface

We are developing a system which is composed of multiple bounded contexts, there are user interfaces where the information displayed needs to be rendered from multiple bounded contexts.
 A classic example of such an interface is the Amazon.com ordering page. Where we see about about the product (product BC), inventory available (Inventory BC), prices and so on
 My question, in such scenarios in which bounded context would the user interface live in ?, I get how we can pull data from multiple BC's to form the page, but are their in guidelines as to where the page itself will reside ?
 Similar questions here http://stackoverflow.com/questions/10911616/composing-bounded-context-on-single-page and here http://stackoverflow.com/questions/23575494/composing-several-bounded-contexts-in-ddd, they deal with how to get information from the multiple BC's, but they do not address in which BC the user interface itself will live in ?
 
 Any guidelines on that ? With an example would be great...