How do you indicate which part(s) of the text a given <topic> or <context> refers to?

CIMI's experience suggests that in a hierarchical scheme like XML you have three choices:

• put a box like <context> around the relevant content
• put a neutral box (like <p> or <seg>) around the content, then tuck the <topic> or <context> just inside it (like a packing slip)
• put the <topic> or <context> somewhere else, and point from it to the relevant context (having first put a box around it)