  Existing knowledge graph (KG) embedding models have primarily focused on
static KGs. However, real-world KGs do not remain static, but rather evolve and
grow in tandem with the development of KG applications. Consequently, new facts
and previously unseen entities and relations continually emerge, necessitating
an embedding model that can quickly learn and transfer new knowledge through
growth. Motivated by this, we delve into an expanding field of KG embedding in
this paper, i.e., lifelong KG embedding. We consider knowledge transfer and
retention of the learning on growing snapshots of a KG without having to learn
embeddings from scratch. The proposed model includes a masked KG autoencoder
for embedding learning and update, with an embedding transfer strategy to
inject the learned knowledge into the new entity and relation embeddings, and
an embedding regularization method to avoid catastrophic forgetting. To
investigate the impacts of different aspects of KG growth, we construct four
datasets to evaluate the performance of lifelong KG embedding. Experimental
results show that the proposed model outperforms the state-of-the-art inductive
and lifelong embedding baselines.
