Method and server for training an Attention-based Neural Network (ANN) to generate a textual output sequence being a content summary to be used as a response to a query. The ANN has an encoder and a decoder sub-network. The method includes, (i) inputting a query and input sequence into the encoder sub-network where the input sequence is a sequence of input groups associated with corresponding content snippets, (ii) generating an encoded representation of the input sequence, which includes generating attention-type outputs for respective words from the input sequence by applying an attention-limiting mask configured to attend only to words from the given input group, (iii) generating a decoded representation being a predicted textual output sequence, (iv) generating a penalty and (iii) adjusting the ANN based on the penalty score.