Task: Question Understanding
Input (English): In this section we describe a number of experiments targeted to compare the performance of popular named entity recognition algorithms on our data. We trained and evaluated Stanford NER, spaCy 2.0, and a recurrent model similar to BIBREF13 , BIBREF14 that uses bidirectional LSTM cells for character-based feature extraction and CRF, described in Guillaume Genthial's Sequence Tagging with Tensorflow blog post BIBREF15 . Stanford NER is conditional random fields (CRF) classifier based on lexical and contextual features such as the current word, character-level n-grams of up to length 6 at its beginning and the end, previous and next words, word shape and sequence features BIBREF16 . spaCy 2.0 uses a CNN-based transition system for named entity recognition. The main model that we focused on was the recurrent model with a CRF top layer, and the above-mentioned methods served mostly as baselines.  
 Question: what ner models were evaluated?
Output (English): Extractive