I am looking at a variant of TSP in which rather than visiting every node, there is a given collection of (possibly overlapping) subset, and the salesman must pass through one node from each subset.
Concretely, I have a graph with vertices $V$ and a family of subsets $S = \{S_1, S_2, ..., S_n \}$. I'm looking for a simple path $\{(v_1, v_2), (v_2, v_3), ..., (v_{m}, v_{1})\}$ such that for all $S_i$, there is a $k$ such that $v_k \in S_i$.
I'm interested in approximation algorithms, and heuristics for computing lower bounds for partial solutions for use in a branch and bound computation. Has this problem been studied elsewhere? If it helps, the problem is metric and the graph is complete.