In recent years, Distributed Ledger Technologies (DLTs) like blockchains have gained much popularity both within industry and research. Today, DLTs are not only perceived as the underlying technology for cryptocurrencies like Bitcoin, but have also been identified as a potential disruptive technology in many different fields, e.g., supply chain tracking and healthcare. In a lot of these fields, blockchains are combined with Internet of Things (|oT) technologies in order to store data from real-world objects in a tamper-proof way, to process this data, and to share the results.

The widespread attention for DLTs has led to manifold research and development activities. These focus either on the application of blockchains in novel use cases, theenhancement of already existing technologies, or the development of completely new DLTs. As a result, today's DLT landscape is heavily fragmented, with different, incompatible technologies being available to potential users. Since interoperability between different blockchains is usually not foreseen in existing protocols and standards, functionalities like sending tokens from one participant to another, invoking and executing smart contracts, or guaranteeing validity of data stored in a blockchain can only be carried out within a single blockchain. This incompatibility contradicts the open nature of |oT- based systems, where heterogeneous technologies interact with each other, and therefore prevents the uptake of blockchains by the industry.

Therefore, the Christian Doppler Laboratory for Blockchain Technologies for the Internet of Things (CDL-BOT) will contribute to the foundations of blockchain interoperability by providing fundamental research results in the areas of cross-blockchain token transfers, cross-blockchain smart contract invocation and interaction, the integration of blockchains with further DLTs and other systems, and by providing client-side blockchain interoperability through developer support. In addition, research in the area of lightweight DLTs for the loT is conducted. While the focus of CDL-BOT is on the application of blockchain technologies in the |oT, other DLTs are also regarded. Furthermore, the research results from the laboratory are not only applicable to the |oT field, but also important for non-|oT-based systems where interoperability between different DLTs is necessary. By doing so, CDL-BOT stimulates a paradigm shift from todays closed blockchains to an open system where devices and users can interact with each other across the boundaries of DLTs.