Playing with name NER

Premise

So, I needed to separate street names that are actual name + surname. Do not ask me why.
Yeah I know that maybe 70% of streets are human names more or less.
So you need 99% precision and at least 30-40% recall.
Or you can imagine a creepy soviet name like Трактор.

So, today making a NER parser is easy, take out our favourite framework (plan PyTorch ofc) of choice.
Even use FastText or something even less true. Add data and boom you have it.

The pain

But not so fast. Turns our there is a reason why cutting out proper names is a pain.
For Russian there is the natasha library, but since it works on YARGY, it has some assumptions about data structure.
I.e. names should be capitalized, come in pairs (name - surname), etc etc - I did not look their rules under the hood, but I would write it like this.

So probably this would be a name - Иван Иванов
But this probably would not ванечка иванофф

Is it bad?
Ofc no, it just assumes some stuff that may not hold for your dataset.
And yeah it works for streets just fine.

Also recognizing a proper name without context does not really work. And good luck finding (or generating) corpora for that.

Why deep learning may not work

So I downloaded some free databases with names (VK.com respects your secutity lol - the 100M leaked database is available, but useless, too much noise) and surnames.
Got 700k surnames of different origin, around 100-200k male and female names. Used just random words from CC + wiki + taiga for hard negative mining.
Got 92% accuracy on 4 classes (just word, female name, male name, surname) with some naive models.

... and it works .... kind of. If you give it 10M unique word forms, it can distinguish name-like stuff in 90% of cases.
But for addresses it is useless more or less and heuristics from natasha work much better.

The moral

- A tool that works on one case may be 90% useless on another;
- Heuristics have very high precision, low recall and are fragile;
- Neural networks are superior, but you should match your artifically created dataset to the real data (it may take a month to pull off properly);
- In any case, properly cracking both approaches may take time, but both heuristics and NNs are very fast to create, but sometimes 3 plain rules give you 100% precision with 10% recall and sometimes generating a fake dataset that matches your domain is a no-brainer. It depends.

#datascience
#nlp
#deeplearning