1. A method comprising: receiving one or more sentences; based on the one or more sentences, generating a tree comprising a plurality of nodes representing the one or more sentences; determining a first set of one or more nodes to remove from the tree; wherein said determining is based, at least in part, on which nodes in the tree comprises a recognized named entity; based on said determining, removing said first set of one or more nodes of the plurality of nodes from the tree; after said removing, reconstructing, from remaining nodes of the plurality of nodes, a first set of one or more sub-sentences of said one or more sentences, wherein the first set of one or more sub-sentences are shorter in length than said one or more sentences; wherein the method is performed by one or more special-purpose computing devices.