UCD vocabulary revision : first iteration of the maintance procedure

[Frederic V. Hessman]

>>  Q | phys.reflectance.bidirectional | Bidirectional reflectance
>>  Q | phys.reflectance.bidirectional.df | Bidirectional reflectance distribution function
> 
> This one is a misunderstanding: "distribution function" is not a subtype of bidirectional reflectance (and has nothing to do with a probability distribution function). Instead, both bidirectional and brdf (= bidirectional reflectance distribution function) are subtypes of reflectance. brdf is a standard acronym in the interested community.
> I suggest instead to have
> Q | phys.reflectance.bidirectional | Bidirectional reflectance (as proposed)
> Q | phys.reflectance.brdf | Bidirectional reflectance distribution function
> If this is an issue, the first one has priority

I don't want to press the issue, but a distribution function is not a reflectance and has everything to do with probabilities in a generic sense, so a "bidirectional reflectance distribution function" must have everything to do with a PDF in the generic sense the UCDs are intended.  The normal uses of UCDs demand that the metadata context be multi-dimensional so that, e.g., the apps know a distribution function is a distribution function, no matter what it is a distribution of.

Rick