# Project a Sequence on a Set

I am reading this paper and looking at Section 2.1:

If $\sigma$ is a sequence over $K$ and $L \subseteq K$, then $\sigma \lceil L$ denotes the sequence obtained by projecting $\sigma$ on $L$.

What exactly does "projecting $\sigma$ on $L$" mean? I've never encountered this set notation before.

• $\sigma\lceil L$ appears to be the sequence obtained from $\sigma$ by dropping out all elements of $K\setminus L$. – Brian M. Scott Nov 1 '15 at 23:57

"$\sigma \lceil L$ appears to be the sequence obtained from $\sigma$ by dropping out all elements of $K \backslash L$."