The vision of the Internet of Things (IoT) promises the capability of connecting billions of devices, resources and things together. In the realisation of this vision, we are currently neglecting the interoperability between devices that is caused by a heterogeneous landscape of things and which leads to the proliferation of isolated islands of custom IoT solutions. A first step towards enabling some interoperability is to connect things to the Web and to use the Web stack, thereby conceiving the socalled Web of Things (WoT). However, even when a homogeneous access is reached through Web protocols, a common understanding is still missing. In addition, decentralised applications, advocated by the IoT vision, and a-priori unknown requirements of specific integration scenarios demand new concepts for the adaptation of things at runtime. Our work focuses on two main aspects: overcoming not only data but also device and interface heterogeneity, and enabling adaptable and scalable decentralised WoT applications. To this end we present an approach for realising decentralised WoT applications based on three main building blocks: 1) semantics of the devices’ capabilities and interfaces, 2) rules to enable embedding controller logic within device’s interfaces for supporting a decentralised applications, and 3) support for reconfiguring the controller logic at runtime for customising and adapting the application. We show how our approach can be applied by introducing a reference architecture, provide a thorough evaluation in terms of a proof-of-concept implementation of an example use case, and performance tests.