*Article* **IoTCrawler: Challenges and Solutions for Searching the Internet of Things**

**Thorben Iggena 1,\*, Eushay Bin Ilyas 1, Marten Fischer 1, Ralf Tönjes 1, Tarek Elsaleh 2, Roonak Rezvani 2, Narges Pourshahrokhi 2, Stefan Bischof 3, Andreas Fernbach 3, Josiane Xavier Parreira 3, Patrik Schneider 3, Pavel Smirnov 4, Martin Strohbach 4, Hien Truong 5, Aurora González-Vidal 6, Antonio F. Skarmeta 6, Parwinder Singh 7, Michail J. Beliatis 7, Mirko Presser 7, Juan A. Martinez 8, Pedro Gonzalez-Gil 6, Marianne Krogbæk 9 and Sebastian Holmgård Christophersen 9**

	- Information and Communication Engineering Department, University of Murcia, 30100 Murcia, Spain; aurora.gonzalez2@um.es (A.G.-V.); skarmeta@um.es (A.F.S.); pedrog@um.es (P.G.-G.)

**Abstract:** Due to the rapid development of the Internet of Things (IoT) and consequently, the availability of more and more IoT data sources, mechanisms for searching and integrating IoT data sources become essential to leverage all relevant data for improving processes and services. This paper presents the IoT search framework IoTCrawler. The IoTCrawler framework is not only another IoT framework, it is a system of systems which connects existing solutions to offer interoperability and to overcome data fragmentation. In addition to its domain-independent design, IoTCrawler features a layered approach, offering solutions for crawling, indexing and searching IoT data sources, while ensuring privacy and security, adaptivity and reliability. The concept is proven by addressing a list of requirements defined for searching the IoT and an extensive evaluation. In addition, real world use cases showcase the applicability of the framework and provide examples of how it can be instantiated for new scenarios.

**Keywords:** Internet of Things; search; security; privacy; reliability; IoT search framework; IoT data sources
