Hello all,

With some time available for LaTeX3, I want to tackle moving xfrac to 
xtemplate before moving on to the harder task of looking at the galley. 
This raises an issue about xtemplate: muskips.

Currently, we have "length" (for a fixed length) and "skip" (for a 
rubber length), but nothing which will map to an underlying muskip. I'm 
not actually sure we should at the design level 
(\DeclareTemplateInterface) but at the code level (\DeclareTemplateCode) 
there needs to be some thought. Possibilities:

  - Introduce a new key type (mathskip ?)
  - Use a keyword in the code section, as we already do for "global":

     keyname1 = math \l_my_muskip       ,
     keyname2 = global math \g_my_muskip,
     keyname3 = global \g_some_other_var,

  - Assume that this is rare enough to use a token list to store in
    input, and sort out the conversion in the code.

Thoughts? At present, (3) is all that is on offer, but perhaps that is 
all we need (do designers care about muskips at all?).
Joseph Wright