The extension of SPARQL in version 1.1 with property paths offers a type of regular path query for RDF graph databases. Such queries are difficult to optimize and evaluate efficiently, however. We have embarked on a project, Waveguide, to build a cost-based optimizer for SPARQL queries with property paths. Waveguide builds a query planwhich we call a waveplan (WP)-which guides the query evaluation. There are numerous choices in the construction of a plan, and a number of optimization methods,

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... the space of plans for a query can be quite large. Execution costs of plans for the same query can vary by orders of magnitude. A WP's costs can be estimated, which opens the way to costbased optimization. We demonstrate that the plan space of Waveguide properly subsumes existing techniques and that the new plans it adds are relevant.