  Social Internet of Things (SIoT), a promising and emerging paradigm that
injects the notion of social networking into smart objects (i.e., things),
paving the way for the next generation of Internet of Things. However, due to
the risks and uncertainty, a crucial and urgent problem to be settled is
establishing reliable relationships within SIoT, that is, trust evaluation.
Graph neural networks for trust evaluation typically adopt a straightforward
way such as one-hot or node2vec to comprehend node characteristics, which
ignores the valuable semantic knowledge attached to nodes. Moreover, the
underlying structure of SIoT is usually complex, including both the
heterogeneous graph structure and pairwise trust relationships, which renders
hard to preserve the properties of SIoT trust during information propagation.
To address these aforementioned problems, we propose a novel knowledge-enhanced
graph neural network (KGTrust) for better trust evaluation in SIoT.
Specifically, we first extract useful knowledge from users' comment behaviors
and external structured triples related to object descriptions, in order to
gain a deeper insight into the semantics of users and objects. Furthermore, we
introduce a discriminative convolutional layer that utilizes heterogeneous
graph structure, node semantics, and augmented trust relationships to learn
node embeddings from the perspective of a user as a trustor or a trustee,
effectively capturing multi-aspect properties of SIoT trust during information
propagation. Finally, a trust prediction layer is developed to estimate the
trust relationships between pairwise nodes. Extensive experiments on three
public datasets illustrate the superior performance of KGTrust over
state-of-the-art methods.
