What is the meaning of this? $$x_i \in \{0,1 \}^{|C|} $$
This is the paper I'm trying to read https://papers.nips.cc/paper/6321-retain-an-interpretable-predictive-model-for-healthcare-using-reverse-time-attention-mechanism.pdf
The notation is in page 2 right at the bottom right.
What would the output X look like? I know that Xi belongs to something, but i'm unsure what it would look like.
The $\tau=|C|$ is a scalar, a positive integer denoting the number of variables (and is possibly equal to the cardinality of some set $C$ which does no matter to us here). Therefore $y\in \{0,1\}^{|C|}$ means all the vectors for which all the entries are binary, i.e.$$y\in \{0,1\}^{|C|}\iff y_i=\text{either 0 or 1}$$