Symbolic AI: The key to the thinking machine

Japan championed Prolog for its Fifth Generation Project, intending to build special hardware for high performance. Similarly, LISP machines were built to run LISP, but as the second AI boom turned to bust these companies could not compete with new workstations that could now run LISP or Prolog natively at comparable speeds. Given that the business isn’t profitable yet, Symbotic stock remains a somewhat speculative investment. On the other hand, the company is valued at under 2.2 times the average analyst estimate target for sales this year. With the business posting such explosive sales growth, that multiple actually looks quite reasonable given the robotics specialist’s feasible path to profitability. Note the similarity to the use of background knowledge in the Inductive Logic Programming approach to Relational ML here.

They can simplify sets of spatiotemporal constraints, such as those for RCC or Temporal Algebra, along with solving other kinds of puzzle problems, such as Wordle, Sudoku, cryptarithmetic problems, and so on. Constraint logic programming can be used to solve scheduling problems, for example with constraint handling rules (CHR). Alain Colmerauer and Philippe Roussel are credited as the inventors of Prolog. Its history was also influenced by Carl Hewitt’s PLANNER, an assertional database with pattern-directed invocation of methods. For more detail see the section on the origins of Prolog in the PLANNER article. The key AI programming language in the US during the last symbolic AI boom period was LISP.

Truly, neurally, deeply

Symbolic AI is reasoning oriented field that relies on classical logic (usually monotonic) and assumes that logic makes machines intelligent. Regarding implementing symbolic AI, one of the oldest, yet still, the most popular, logic programming languages is Prolog comes in handy. Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages. Symbolic AI is a sub-field of artificial intelligence that focuses on the high-level symbolic (human-readable) representation of problems, logic, and search. For instance, if you ask yourself, with the Symbolic AI paradigm in mind, “What is an apple?

But it can be challenging to reuse these deep learning models or extend them to new domains. For organizations looking forward to the day they can interact with AI just like a person, symbolic AI is how it will happen, says tech journalist Surya Maddula. After all, we humans developed reason by first learning the rules of how things interrelate, then applying those rules to other situations – pretty much the way symbolic AI is trained.

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If one of the first things the ducklings see after birth is two objects that are similar, the ducklings will later follow new pairs of objects that are similar, too. Hatchlings shown two red spheres at birth will later show a preference for two spheres of the same color, even if they are blue, over two spheres that are each a different color. Somehow, the ducklings pick up and imprint on the idea of similarity, in this case the color of the objects.

Critiques from outside of the field were primarily from philosophers, on intellectual grounds, but also from funding agencies, especially during the two AI winters. A more flexible kind of problem-solving symbolic ai occurs when reasoning about what to do next occurs, rather than simply choosing one of the available actions. This kind of meta-level reasoning is used in Soar and in the BB1 blackboard architecture.

Full logical expressivity means that LNNs support an expressive form of logic called first-order logic. This type of logic allows more kinds of knowledge to be represented understandably, with real values allowing representation of uncertainty. Many other approaches only support simpler forms of logic like propositional logic, or Horn clauses, or only approximate the behavior of first-order logic. One of the main stumbling blocks of symbolic AI, or GOFAI, was the difficulty of revising beliefs once they were encoded in a rules engine. Expert systems are monotonic; that is, the more rules you add, the more knowledge is encoded in the system, but additional rules can’t undo old knowledge.

The technology actually dates back to the 1950s, says expert.ai’s Luca Scagliarini, but was considered old-fashioned by the 1990s when demand for procedural knowledge of sensory and motor processes was all the rage. Now that AI is tasked with higher-order systems and data management, the capability to engage in logical thinking and knowledge representation is cool again. Natural language processing focuses on treating language as data to perform tasks such as identifying topics without necessarily understanding the intended meaning. Natural language understanding, in contrast, constructs a meaning representation and uses that for further processing, such as answering questions. Knowledge-based systems have an explicit knowledge base, typically of rules, to enhance reusability across domains by separating procedural code and domain knowledge.

A closer look into the history of combining symbolic AI with deep learning

One difficult problem encountered by symbolic AI pioneers came to be known as the common sense knowledge problem. In addition, areas that rely on procedural or implicit knowledge such as sensory/motor processes, are much more difficult to handle within the Symbolic AI framework. In these fields, Symbolic AI has had limited success and by and large has left the field to neural network architectures (discussed in a later chapter) which are more suitable for such tasks. In sections to follow we will elaborate on important sub-areas of Symbolic AI as well as difficulties encountered by this approach.

Data fabric developers like Stardog are working to combine both logical and statistical AI to analyze categorical data; that is, data that has been categorized in order of importance to the enterprise. Symbolic AI plays the crucial role of interpreting the rules governing this data and making a reasoned determination of its accuracy. Ultimately this will allow organizations to apply multiple forms of AI to solve virtually any and all situations it faces in the digital realm – essentially using one AI to overcome the deficiencies of another. When deep learning reemerged in 2012, it was with a kind of take-no-prisoners attitude that has characterized most of the last decade.

Similar to the problems in handling dynamic domains, common-sense reasoning is also difficult to capture in formal reasoning. Examples of common-sense reasoning include implicit reasoning about how people think or general knowledge of day-to-day events, objects, and living creatures. It has now been argued by many that a combination of deep learning with the high-level reasoning capabilities present in the symbolic, logic-based approaches is necessary to progress towards more general AI systems [9,11,12].

The framework introduces a set of polymorphic, compositional, and self-referential operations for data stream manipulation, aligning LLM outputs with user objectives. As a result, we can transition between the capabilities of various foundation models endowed with zero- and few-shot learning capabilities and specialized, fine-tuned models or solvers proficient in addressing specific problems. In turn, the framework facilitates the creation and evaluation of explainable computational graphs. We conclude by introducing a quality measure and its empirical score for evaluating these computational graphs, and propose a benchmark that compares various state-of-the-art LLMs across a set of complex workflows. We refer to the empirical score as the “Vector Embedding for Relational Trajectory Evaluation through Cross-similarity”, or VERTEX score for short.