I'm working with RNNs and during research I found many mentions of alignment between input and output.
For example (Sutskever et al., 2014):
The RNN can easily map sequences to sequences whenever the alignment between the inputs the outputs is known ahead of time. However, it is not clear how to apply an RNN to problems whose input and the output sequences have different lengths with complicated and non-monotonic relationships.
Now, I think that the alignment issue means that one time step in the input not necessarily maps to output on the same time step, but I am not sure if this explanation is correct. I can not find any good resources for explaining how alignment between input and output and just what that means. Any help or explanation is much appreciated.