Difference between a research gap and a challenge While reading about an article on computer science field I stumbled upon a question regarding the difference between a research gap and a challenge. 

To my current knowledge, research gap is an unsolved or untouched area within a field of study. For research challenge, it seems to be a difficult to solve or answer question. 

What are your opinions / answers from experience so that I have a better understanding?
It is a bit hard to judge as the phrasing may be due to an individual. But I would think that a research gap would be an unsolved part of some area of a field that has been studied fairly extensively and needs the gap filled to advance in some particular direction. 

On the other hand, a research challenge is broader. It would be a request for study of some problem that has been neglected by the research community either because it has just been overlooked or because no one has yet thought it important enough to tackle. 

Filling a research gap may be difficult, but it is relatively constrained with much work surrounding it already done. A research challenge however requires a much more extensive attack and probably many more resources. It is intended to open new lines of inquiry.