  Knowledge Graphs (KGs) have been applied to many tasks including Web search,
link prediction, recommendation, natural language processing, and entity
linking. However, most KGs are far from complete and are growing at a rapid
pace. To address these problems, Knowledge Graph Completion (KGC) has been
proposed to improve KGs by filling in its missing connections. Unlike existing
methods which hold a closed-world assumption, i.e., where KGs are fixed and new
entities cannot be easily added, in the present work we relax this assumption
and propose a new open-world KGC task. As a first attempt to solve this task we
introduce an open-world KGC model called ConMask. This model learns embeddings
of the entity's name and parts of its text-description to connect unseen
entities to the KG. To mitigate the presence of noisy text descriptions,
ConMask uses a relationship-dependent content masking to extract relevant
snippets and then trains a fully convolutional neural network to fuse the
extracted snippets with entities in the KG. Experiments on large data sets,
both old and new, show that ConMask performs well in the open-world KGC task
and even outperforms existing KGC models on the standard closed-world KGC task.
