ABSTRACT
With the uptake of Linked Data in recent years, the topic of integrated querying over multiple distributed data sources has attracted significant attention. In order to join information provided by different sources, efficient query processing strategies are required, the major challenge lying in the natural distribution of the data. Regarding this challenge, state-of-the-art approaches can be divided into three main categories: materialization-based query pro-
cessing (MQP), lookup-based query processing (LQP), and federated query processing (FQP).
