Best way of picking up data two levels up?   

I have three levels of specifications - A spec, B spec, C spec. Each spec is in its own module and there are links showing the relationship of the requirements between the A spec and the B spec and then between the B spec and the C spec. I believe this is a fairly standard setup.

I have a DXL attribute in the B spec that gets the A spec requirement IDs that map to the B spec requirements. I also have a similar DXL attribute in the C spec showing the B spec requirement IDs mapping to the C spec requirements. In the C spec, I would like to show the A spec requirement IDs that map to the B spec requirements that map to the C spec requirements. The two ways I see to do this are
1. follow the link from the C spec to the B spec and then follow the link from the B spec to the A spec to get the A spec IDs
2. follow the link from the C spec to the B spec and then use the DXL attribute in the B spec that has the A spec IDs

The second way is easier from a coding standpoint, but I wasn't sure if there were some gotchas with the second option, and I would like input/opinion from those of you that have more DXL and DOORS experience than I.

Thanks,
Marjorie

Your answer tells me how to easily get the dxl code using the DOORS tools, but it does not really answer my question about whether there are gotchas with the second method using the dxl attribute in the B spec.

There is no functional difference between both approaches, assuming you use the same DXL code for following the links between the modules. But there are some design decisions you should make:

If a module links to several other modules there might be the need to follow only some special link paths. Example

If you have a link setup like this (A,B,C,D, E = modules):

A - B - D 
 \    / 
  \  / 
   C
  / 
 / 
E

Sometimes you want to follow only a special link path (e.g. D->B->A) which is easy with DXL attributes but sometimes you want to follow all link paths (D-B-A and D-C-A). If you use DXL attributes in this case, you will need to combine the values of DXL attributes in C and B to one value. But C needs now two different DXL attributes, because you may not want links to E to appear. Therefore you need to maintain a lot of DXL attributes.
And what happens if another link path to A will be created later? You will need to modify the DXL attribute in D.

So you should really answer the question about how stable you link setup will be and if you want to follow only one special path from a module to another or maybe ALL paths.

Regards, Mathias