Is Russian Grammar Uniform? Norm, usage, and variation [Едина ли русская грамматика? Норма, узус, варианты]

This is a presentation of my talk given at the conference "Grammatical processes and systems in synchrony and diachrony" (In memory of Andrej A. Zaliznjak), Moscow, Vinogradov Institute of the Russian Language, RAS, 27-29 May, 2019, http://www.ruslang.ru/doc/program_grammar2019.pdf

I claim that grammar as a basic component of a natural language is equivalent to a set of constraints which can be parametrized. Grammar in the specified sense is always uniform and non-contradictory, but this fact is obscured by language-internal variation, especially by the existence of idioms or 'grammatical pseudo-dialects' with different parameter settings.