Before revision:  In the contextualization step, we use LMs to generate many left and right contexts which collectively capture the meaning of the input sentence. Then , in the reflection step we decode in the semantic neighborhood of the input, conditioning on an ensemble of generated contexts with the reverse direction LM.
After revision:  In the contextualization step, we use LMs to generate many left and right contexts which collectively capture the input (e.g. the source sentence for paraphrasing). Second , in the reflection step we decode in the semantic neighborhood of the input, conditioning on an ensemble of generated contexts with the reverse direction LM.