As shown in Figure FIGREF7 , KAR is an end-to-end MRC model consisting of five layers:

Lexicon Embedding Layer. This layer maps the words to the lexicon embeddings. Context Embedding Layer. This layer maps the lexicon embeddings to the context embeddings. Coarse Memory Layer. This layer maps the context embeddings to the coarse memories. Refined Memory Layer. This layer maps the coarse memories to the refined memories. Answer Span Prediction Layer. This layer predicts the answer start position and the answer end position based on the above layers. 
 Question: What type of model is KAR?
Lexicon Embedding Layer Context Embedding Layer Coarse Memory Layer Refined Memory Layer Answer Span Prediction Layer