These excerpts were recorded at Michael Swan's British Council Seminar held in London in spring 2010. You can also read a review of this event on the BC Seminars blog.
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Time and tense discrepancies in English ( and probably other languages) grammar make the language more complicated. The terminologies used do not always match.
"what are you doing these days?" "I am writing a book". ( It does not necessarily talk about the activity going on at the moment of speaking).
"How are you feeling?" "How do you feel?" (They can be used to talk about the present state).
John and Mary are getting married.( The present progressive tense is used to talk about a future event).
Therefore, I think emerging grammars may be able to facilitate the description of language. But there will never be one to provide us with a comprehensive view of language due to its volatile nature.