From the discussion, and the proposals I made to some of the items, it follows we might need the following new UCDs:

• meta.bib.doi, for supporting DOI-based bibliographical references; not very needed, if the corresponding field only allows for bibcodes. This would be used for field bib_reference.
• pos.uv, for specifying a UV-plane axis, and pos.uv.u and pos.uv.v for specifying a locus in the UV plane. This would be used for field s_ucd, and in general for fields with UType Char.SpatialAxis.UCD. In particular:
  • pos.uv should be a Secondary keyword, as pos.eq et al.
  • pos.uv.u and pos.uv.v can be used as Primary or Secondary UCDs, as pos.eq.ra et al.
• arith.fft, for qualifying a UCD as being subject to a FFT transform. This would be used for field em_axis (for instance, em.freq; arith.fft for an autocorrelation series), or for field s_ucd, if instead of pos.uv, pos.eq; arith.fft were preferred. It should be used only as a Secondary UCD.
• arith.log, for qualifying a UCD as being subject to a logarithmic transform. This would be used for field em_axis (for instance, em.wl; arith.log; this use case comes from the SSA Recommendation). It should be used only as a Secondary UCD.
• instr.footprint, analogous to instr.fov. It should be used only as a Secondary UCD. It is needed to support s_region.

-- JuanDeDiosSantanderVela - 08 Mar 2011