This work deals with the last-generation distributed data aggregation service (DDAS), which addresses requirements “not only in terms of ... performance, cost, availability, reliability,” and scale, “but also in terms of computer-human interaction and ease of programming.” DDAS is a key management task behind cloud services that proposes several challenges and tradeoffs in terms of accuracy, reliability, messaging, and time complexity.

The paper proposes a formal method based on retrieval and aggregation rules expressed in Rule Markup Language (RML). The system engine matches the rules to “the structured data in order to obtain the unstructured entries from ... [the] data storage system,” simplifying the retrieval process.

This contribution is definitely interesting and looks suitable for a large audience. Moreover, the paper is well written: the introduction is clear, the section on related work is well structured, the contribution is clearly described, and the results are discussed in a realistic context. Future works look promising.