Symbolic AI And Search
Early AI treated intelligence as searching for solutions in spaces governed by explicit rules, laying foundations for planning, games, and pathfinding.
Overview
Start with the chapter spine for an era-level frame, then use papers, systems, data, compute, and standards to explain why the field changed direction. The selection is representative, not exhaustive.
Chapter Spine
Early AI treated intelligence as searching for solutions in spaces governed by explicit rules, laying foundations for planning, games, and pathfinding.
Expert knowledge was written as if-then rules. The systems were explainable, but acquiring knowledge and maintaining exceptions became bottlenecks.
AI moved from deterministic rules toward uncertainty modeling, updating beliefs with evidence and gradually adopting data-driven learning.
Support vector machines, tree models, and ensembles learned decision boundaries from examples, moving AI further from hand-written rules toward data-driven methods.
Convolutional networks combine visual features layer by layer, from edges and textures to shapes, using local receptive fields and shared parameters.
Systems use observations, rewards, and returns after actions to change value estimates or policies, often in combination with search and deep representations.
Attention creates direct connections between tokens and became a key architecture for large language and multimodal models.
Scaled pretraining produces a general base model, while instruction tuning and preference feedback further shape user-facing behavior.
Large language models have powerful generation capabilities, but modern applications usually organize them with context, tools, memory, and evaluation.
RAG retrieves external knowledge into the context, improving factuality, freshness, and citation value.
An LLM enters a loop of planning, tool calls, observation, and revision, allowing it to execute multi-step tasks instead of only answering once.
Red-team cases, guardrails, least privilege, human review, and regression evaluation turn a failure into a repeatable test that constrains later releases.
Source-backed Milestones
Every event links to chapters, lineage nodes, and at least one primary paper, book, official record, or standard. Impact notes focus on downstream mechanisms without treating one event as the sole cause.
Causal Explorer
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Computing Machinery and Intelligence used the imitation game to discuss machine intelligence, shifting an abstract argument toward observable behavioral evidence.
It did not define intelligence completely, but established a recurring AI pattern: specify the task first, then debate the evidence.
The 1955 proposal for the 1956 summer project named language, abstraction, problem solving, self-improvement, and neural nets as research problems.
It gathered computing, logic, and neural research under one label while exposing the lasting tension between ambitious goals and available capability.
Rosenblatt described a probabilistic model of a hypothetical nervous system that could adjust connections from input and perform recognition.
Learned weights replaced some hand-written rules, while the limits of a single layer later motivated work on multilayer representations.
Samuel combined search, position evaluation, and learning, reporting a program that could play better checkers than its author.
Machine learning became an implemented mechanism: experience could update an evaluation function and alter later search choices. This atlas does not retroactively label the early combination as the complete reinforcement-learning paradigm later formalized.
SRI's mobile robot, researched from 1966 to 1972, could perceive its surroundings, plan routes, and rearrange simple objects.
It moved graph search and planning into a constrained physical world and exposed the engineering cost of real perception and action.
Hart, Nilsson, and Raphael showed how domain heuristics could enter graph search and established an optimality property for a class of strategies.
Search no longer meant only blind enumeration: path cost and an estimate could jointly guide expansion under explicit conditions.
The report argued that many early promises had not been met and highlighted combinatorial explosion as a barrier to scaling general systems.
It is representative primary evidence for the first AI-winter context; this atlas treats it as one UK review, not the single cause of a global downturn.
MYCIN used rules, certainty factors, and explanation mechanisms for a constrained infectious-disease consultation problem.
Expert systems showed the power of narrow domain knowledge while turning knowledge acquisition, exceptions, and accountability into new bottlenecks.
Rumelhart, Hinton, and Williams described repeatedly adjusting connection weights from output error.
Multilayer networks could form intermediate features instead of relying only on hand-designed inputs, providing a key mechanism for the later deep-learning revival.
Pearl systematized directed graphs for conditional dependence, evidence propagation, and probabilistic reasoning.
Probability updating grew from an isolated formula into a structured framework combining knowledge, dependencies, and uncertainty.
Watkins and Dayan described an incremental method for learning optimal action values and established convergence under the repeated-sampling and representation conditions stated in the paper.
Outcome feedback can update state-action values without a target action at every step. The theorem does not make every reinforcement-learning method or finite teaching demo converge.
Cortes and Vapnik mapped inputs into high-dimensional feature spaces and used support vectors to determine a classification boundary.
Classical machine learning linked optimization, boundary capacity, and generalization, becoming a major high-performance route before deep learning.
IBM's system combined specialized search, evaluation, and massive parallel computation to defeat Garry Kasparov in a six-game match in 1997.
The win showed that search and compute could exceed humans in a narrow task, not that the system had acquired general intelligence.
The paper compared handwriting-recognition methods and described convolutional networks plus global training in cheque-reading systems.
Local connectivity and shared parameters moved from mechanisms into deployed engineering, providing reusable structure for larger vision networks.
ImageNet organized large-scale image data with the WordNet hierarchy, supporting object-recognition training and comparable evaluation.
Data scale and a common task made progress measurable and prepared the conditions for a compute-intensive deep-vision race.
The 2012 system trained a deep convolutional network on about 1.2 million images with an efficient GPU implementation and sharply reduced ImageNet error.
When algorithm, data, and compute arrived together, deep learning shifted from a long-running research route to mainstream vision engineering.
The paper used a deep convolutional network, experience replay, and Q-learning to learn control policies for multiple Atari games from pixel input.
Deep representations let value learning handle high-dimensional sensory input, while Atari results did not establish general intelligence or reliable real-world control.
The system combined policy networks trained with supervised and reinforcement learning, value networks, and Monte Carlo tree search.
It showed that learned representations and classical search can cooperate rather than replace one another; reinforcement learning did not produce the result in isolation from supervised learning and search.
The paper proposed a sequence-transduction architecture based only on attention, removing recurrence and convolution while improving training parallelism.
Direct token connections and parallel training became key structural preconditions for scaling foundation models.
Within the study's scope, cross-entropy loss followed power-law relationships with model size, dataset size, and training compute.
Scaling became a measurable engineering direction, while lower training loss alone did not establish reliability, safety, or alignment with user intent.
The 175-billion-parameter model performed many tasks from instructions and examples in its prompt without updating its weights.
The capability interface shifted partly from task-specific fine-tuning to general text interaction, increasing the importance of data, evaluation, and system constraints.
RAG used a neural retriever over a dense Wikipedia index and conditioned generation on retrieved passages.
Knowledge updates, provenance, and generation could become separate system components instead of putting every fact into model parameters.
The study further tuned a pretrained language model on tasks described by natural-language instructions and evaluated zero-shot performance on unseen tasks.
Post-training began to shape behavior around recognizing requests and following task formats instead of only enlarging the pretrained model.
The study first used labeler demonstrations for supervised fine-tuning, then used candidate-output rankings to train a reward model and optimized the policy further with PPO.
Preferences under specific tasks, labeling instructions, and evaluation distributions shaped behavior, while the paper documented simple mistakes and unresolved limits. Preferences are not universal truth, and RLHF is not all post-training.
The method alternated language-model reasoning, calls to external sources, observations, and plan updates.
An agent's core is not merely producing a plan; observations must keep changing the next action.
AI RMF 1.0 organized lifecycle risk management into Govern, Map, Measure, and Manage functions.
Safety and reliability expanded from one-time testing into an organizational process spanning design, deployment, monitoring, and review.
The Generative AI Profile mapped red teaming, incident records, ongoing evaluation, and treatment of risk onto the AI RMF.
Release gates for modern generative systems need repeatable evidence and ongoing monitoring; one passing run cannot prove that risk is gone.