Symbolic, Distributed and Distributional Representations for Natural Language Processing in the Era of Deep Learning: a Survey

Natural language and symbols are intimately correlated. Recent advances in machine learning (ML) and in natural language processing (NLP) seem to contradict the above intuition: symbols are fading away, erased by vectors or tensors called distributed and distributional representations. However, there is a strict link between distributed/distributional representations and symbols, being the first an approximation of the second. A clearer understanding of the strict link between distributed/distributional representations and symbols will certainly lead to radically new deep learning networks. In this paper we make a survey that aims to draw the link between symbolic representations and distributed/distributional representations. This is the right time to revitalize the area of interpreting how symbols are represented inside neural networks.