69 - Relation Extraction

Relationship extraction is the task of extracting semantic relationships from a text. A relation can be defined as a connection between entities. There are different ways of extracting relations:

• Simple deduction: use the presence of two entities in the same sentence (or paragraph) as an unnamed relation.
• Predicate logic: use the Dependency tags to define semantic relation-queries like (subject, verb, object) where the verb defines the relation.
• Hearst Patterns: use the POS-tags to extract Hearst Patterns, which are hierarchical relations based on semantic information. Hearst Patterns are used to extract hypernym relations. A hyponym (e.g. Shakespeare) is in a type-of relationship with its hypernym (e.g. author). These are important for extracting tuples for ontologies.

• Word2vec similarity: use vector calculations to define relations, like in Gensim:

    import gensim 

    model = gensim.models.Word2Vec.load('model-01')  
    model.most_similar(positive=[' **father** ', ' **son** '], negative=[' **mother** ']) 

    >>> [(' **daughter** ', 0.8783684968948364)] 

• Question Answering and Slot Filling: ask a question in a certain relationship-template and use the answer to fill the slot.

    Template: husband_of = ”Who is the husband of [PERSON]?”  
    Question: ”Who is the husband of Michelle?”  
    Answer  : ”Barack”  
    Relation: Barack --> husband_of --> Michelle 

• Transformer for Relation Extraction: Use deeplearning for relation extraction. TACRED, with 106k sentence-level examples and 41 relation types, and DocRED, with 107k document-level examples and 96 relation types, are good relation extraction datasets to train models on.

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