  Regular path queries (RPQs) the ubiquitous mechanism for querying data graphs
of partially known structure. RPQs are in essence regular expressions over the
edge symbols. The answer to an RPQ on a given graph (database) is the set of
pairs of objects, which are connected by paths spelling words in the language
of the regular path query. Often the database edges come with a weights
assoaciated to them. Such weights can distances, levels of discomfort,
multiplicities, etc. We model weights using semiring frameworks.
