Joint Multi-Facts Reasoning Network For Complex Temporal Question Answering Over Knowledge Graph

Temporal Knowledge Graph (TKG) is an extension of regular knowledge graph by attaching the time scope. Existing temporal knowledge graph question answering (TKGQA) models solely approach simple questions, owing to the prior assumption that each question only contains a single temporal fact with explicit/implicit temporal constraints. Hence, they perform poorly on questions which own multiple temporal facts. In this paper, we propose $\underset{‾}{\mathbf{\text{J}}}$oint $\underset{‾}{\mathbf{\text{M}}}$ulti $\underset{‾}{\mathbf{\text{F}}}$acts $\underset{‾}{\mathbf{\text{R}}}$easoning $\underset{‾}{\mathbf{\text{N}}}$etwork (JMFRN), to jointly reasoning multiple temporal facts for accurately answering \emph{complex} temporal questions. Specifically, JMFRN first retrieves question-related temporal facts from TKG for each entity of the given complex question. For joint reasoning, we design two different attention (\ie entity-aware and time-aware) modules, which are suitable for universal settings, to aggregate entities and timestamps information of retrieved facts. Moreover, to filter incorrect type answers, we introduce an additional answer type discrimination task. Extensive experiments demonstrate our proposed method significantly outperforms the state-of-art on the well-known complex temporal question benchmark TimeQuestions.