  Recent advances in personalized recommendation have sparked great interest in
the exploitation of rich structured information provided by knowledge graphs.
Unlike most existing approaches that only focus on leveraging knowledge graphs
for more accurate recommendation, we perform explicit reasoning with knowledge
for decision making so that the recommendations are generated and supported by
an interpretable causal inference procedure. To this end, we propose a method
called Policy-Guided Path Reasoning (PGPR), which couples recommendation and
interpretability by providing actual paths in a knowledge graph. Our
contributions include four aspects. We first highlight the significance of
incorporating knowledge graphs into recommendation to formally define and
interpret the reasoning process. Second, we propose a reinforcement learning
(RL) approach featuring an innovative soft reward strategy, user-conditional
action pruning and a multi-hop scoring function. Third, we design a
policy-guided graph search algorithm to efficiently and effectively sample
reasoning paths for recommendation. Finally, we extensively evaluate our method
on several large-scale real-world benchmark datasets, obtaining favorable
results compared with state-of-the-art methods.
