Hi,

> <section id="foo"><!-- *1 -->
>   <anchor id="a"><!-- *2 -->
>   <section><!-- *3 -->
>     <anchor id="b"><!-- *4 -->
>   </section>
> </section>
> 
> How can I define a template for the "anchor" so that I can 
> test if the 
> first "anchor" inside the immediate ancestral "section" is 
> the current 
> "anchor" node?
> 
> For example, when I'm processing *4, I want to test if the 
> first anchor 
> element inside its immediate ancestral section (*3) is itself (*4). 

(I had to read the sentence quite a few times, so I may have misunderstood your problem.) Test if it has preceding anchor siblings:

  not(preceding-sibling::anchor)

Cheers,

Jarno