Salesforce research

For each generated word, the model pays attention to specific words of the input and the previously generated output. Automatic summarization models can work in one of two ways: by extraction or by abstraction. Extractive models perform "copy-and-paste" operations: they select relevant phrases of the input document and concatenate them to form a summary. They are quite robust since they use existing natural-language phrases that are taken straight from the input, but they lack in flexibility since they cannot use novel words or connectors. They also cannot paraphrase like people sometimes do.