Ever wondered why links in the BizTalk mapper can be labelled (BizTalk Server 2004 of course :) )?
Well, create a new map in BizTalk and add the string concat functoid. Drag and drop a couple of links from your source fields to the functoid.
Now open the functoid parameter dialog. You will see your source fields as xpath expressions, no problem for a techie but still not that readable.
If you label your links they will appear in the functoid parameter dialog, making the arguments of your functioid easier to read. Cool.
Now let's look at an example that makes labelling your links really useful!
Remove the source links of the string concat functiod, and add a couple of uppercase functoids as inputs for your concat functoid by linking them.
Now open up the concat functoid's arguments dialog. You will see three arguments, each as "Uppercase". Just think about opening up an existing map and trying to find out which argument will be appended to another?! No way.
Now label the links between the uppercase and concat functoid. Open the arguments dialog box. Now you can see which argument will be appended first, etc... Cool!