The paper "Efficient Evaluation and Approximation of Well-designed Pattern Trees", coauthored by researcher Pablo Barceló from the CSWR, has been accepted at the 34th ACM Symposium on Principles of Database Systems (PODS 2015), which will be held in Melbourne, Australia, in June 2015. This is the most important venue worldwide in the area of foundations of databases. The paper develops a thorough study of which fragments of the most basic pattern languages for the Semantic Web can be evaluated efficiently. It also develops a theory of approximations for these languages that allows to find quick answers to queries when exact evaluation is computationally hard. The article is also coauthored by Reinhard Pichler and Sebastian Skritek from the Technical University of Vienna, who visited our group during September to work on the paper.