2. I wish NTCIR corpus is not that difficult to download (I once wrote a request for NTCIR corpus, but no one replies), please make it public accessible just like what MIaS does: https://mir.fi.muni.cz/mias/
3. My search engine (http://tkhost.github.io/opmes) is actually using structural method, but I still give up MathML and go parsing TeX directly instead. Why? In TeX I can just omit irrelevant command like "\color" and "\mbox", and only focus on a handful math-related TeX subset, and the result is great. Although my search engine can just handle "toy formula syntax", but maybe it is better than MathWebSearch (https://zbmath.org/formulae/) and even beat Tangent (http://saskatoon.cs.rit.edu/tangent/random) in long query. But in MathML, I have no idea why I need to read its lengthy spec, and I see no reason to write a MathML parser.
NTCIR-math conference (and its none-friendly website) makes me unwilling to submit a single paper.