Sign Synthesis Technology: Underlying Linguistic Description

What are some candidates for the underlying linguistic description?

1. Stokoe (Stokoe et al. 1965)/ASCII-Stokoe (Mandel 1993) (incomplete)
2. Newkirk 1986/SignFont (Newkirk 1987) (mid-level)
3. HamNoSys/GML/SiGML (Bangham et al. 2000; Elliott et al 2000)
4. SignWriting/SWML (Rocha 2000)