Computational Logic in Artificial Neural Networks

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The fundamental problem of creating (and then evaluating) automated reasoning systems based upon formally defined logical calculi has been considered for centuries. Arguably, the problem is as old as mathematical logic and even computational mathematics.Among the pioneers in this field were Boole, Peano and Hilbert. Hilbert, in his attempts to find proper foundations of mathematics and a proper formal calculus for it, announced the programme of formalising mathematics using a logical calculus. This program is now commonly called Hilbert's Programme . However, in his well-known Incompleteness Theorem [1931], Gdel proved that, in every sufficiently strong formal system, there is an undecidable proposition. It follows that Hilbert's programme cannot be accomplished, as shown by Church and Turing. However, even after these results, the major question, of how one can create some kind of automated reasoning, or, as it was later called, artificial intelligence, remained of interest. It is an open question whether the human mind acts in accordance with some pre-defined algorithm, whether this algorithm is sound, whether it can be soundly formalised by humans, and whether, if formalised, it can be shown to be sound. Turing's machines stimulated the creation of digital computers; biology and neuroscience became proper scientific disciplines. All this progress increased interest in the general problem of creating a form of artificial intelligence.Connectionism is a movement in the fields of artificial intelligence, cognitive science, neuroscience, psychology and philosophy of mind which hopes to explain human intellectual abilities using the idea of an artificial neural network / a simplified mathematical model of a human brain. One of its areas, Neuro-Symbolic Integration, investigates ways of integrating logic and formal languages with neural networks in order to better understand the essence of symbolic (deductive) and human (developing, spontaneous) reasoning, and to show interconnections between them.Many neuro-symbolic systems have been proposed over the last two decades. However, they have been little used in automated reasoning and computational logic. Now is the right time for development of an alternative to the existing neuro-symbolic networks; for this, our proposed SLD neural networks appear to be a most suitable candidate. SLD neural networks use a novel method of performing the algorithm of first-order SLD-resolution for classical logic programs in neural networks. The resulting neural networks are finite, and embody six learning functions as recognised in neurocomputing.We propose to test our SLD neural networks and apply them to a broader class of logic programs and logics. This will lead us to evaluate their effectiveness, comparing them with orthodox methods used in automated reasoning, on the one hand, and with alternative (non-neural) networks used in computational logic, on the other hand. The culmination of the project will be the creation of a more general, and more abstract, neural network interpreter ready to be used as an automated prover for a broad class of logics and logic programs. By achieving its objectives, the project will have a long-term effect of stimulating research in the areas of Neuro-Symbolic Integration and Cognitive Science.