Description of quality of a transformation

[Victor Porton <porton@narod.ru>]

I am writing a draft of a specification of transformations between XML namespaces. Transformations can be chained:

A->B->C (where A, B, C are namespaces).

I need to describe criteria for selecting chains of transformations among several possible variants.

One characteristic of a transformation is its "quality". We may denote it "release", "beta", "alpha" or something like this. Or we may use a numeric quality (something like 0.6=alpha, 0.9=beta, 1=release)?

What should we prefer numeric quality or a scheme like "release", "beta", "alpha"? With numeric quality we could do some calculations, but it is unclear whether these calculations are meaningful.

What else criteria for choosing a chain of several transformation should we consider?

Should we describe reversible/non-reversible transformations? At first this seems a promising idea. But is it? In fact most of XML transformations are in practice not reversible. So is it worth to bother to mark some transformations reversible?

Any other idea about how to describe transformations?

-- 
Victor Porton - http://portonvictor.org