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Title: RelWalk -- A Latent Variable Model Approach to Knowledge Graph Embedding

Paper content:
Knowledge Graph Embedding (KGE) is the task of jointly learning entity and relation embeddings for a given knowledge graph.
Existing methods for learning KGEs can be seen as a two-stage process where
(a) entities and relations in the knowledge graph are represented using some linear algebraic structures (embeddings), and
(b) a scoring function is defined that evaluates the strength of a relation that holds between two entities using the corresponding relation and entity embeddings.
Unfortunately, prior proposals for the scoring functions in the first step have been heuristically motivated, and it is unclear as to how the scoring functions in KGEs relate to the generation process of the underlying knowledge graph.
To address this issue, we propose a generative account of the KGE learning task.
Specifically, given a knowledge graph represented by a set of relational triples (h, R, t), where the semantic relation R holds between the two entities h (head) and t (tail), we extend the random walk model (Arora et al., 2016a) of word embeddings to KGE.
We derive a theoretical relationship between the joint probability p(h, R, t) and the embeddings of h, R and t.
Moreover, we show that marginal loss minimisation, a popular objective used by much prior work in KGE, follows naturally from the log-likelihood ratio maximisation under the probabilities estimated from the KGEs according to our theoretical relationship.
We propose a learning objective motivated by the theoretical analysis to learn KGEs from a given knowledge graph.
The KGEs learnt by our proposed method obtain state-of-the-art performance on FB15K237 and WN18RR benchmark datasets, providing empirical evidence in support of the theory.
Knowledge graphs such as Freebase BID2 organise information in the form of graphs, where entities are represented by vertices in the graph and the relation between two entities is represented by the edge that connects the corresponding two vertices.
By embedding entities and relations that exist in a knowledge graph in some (possibly lower-dimensional and latent) space we can infer previously unseen relations between entities, thereby expanding a given knowledge graph BID11 BID20 Lin et al., 2015; BID9 BID16 BID17 BID4 .Existing
KGE methods can be seen as involving two main steps. First, given
a knowledge graph represented by a set of relational triples (h, R, t), where a semantic relation R holds between a head entity h and a tail entity t, entities and relations are represented using some mathematical structures such as vectors, matrices or tensors. Second, a scoring
function is proposed that evaluates the relational strength of a triple (h, R, t) and entity and relation embeddings that optimise the defined scoring function are learnt using some optimisation method. Table 1 shows some
of the scoring functions proposed in prior work in KGE learning.Despite the wide applications of entity and relation embeddings created via KGE methods, the existing scoring functions are motivated heuristically to capture some geometric requirements of the embedding space. For example, TransE
BID4 assumes that the entity and relation embeddings co-exist in the same (possibly lower dimensional) vector space and translating (shifting) the head entity embedding by the relation embedding must make it closer to the tail entity embedding, whereas ComplEx BID16 ) models the asymmetry in relations using
We proposed RelWalk, a generative model of KGE and derived a theoretical relationship between the probability of a triple and entity, relation embeddings.
We then proposed a learning objective based on the theoretical relationship we derived.
Experimental results on a link prediction and a triple classification tasks show that RelWalk obtains strong performances in multiple benchmark datasets.

assistant: text: We present a theoretically proven generative model of knowledge graph embedding.