AskDefine | Define AI

Dictionary Definition



1 an agency of the United States Army responsible for providing timely and relevant and accurate and synchronized intelligence to tactical and operational and strategic level commanders [syn: Army Intelligence]
2 the branch of computer science that deal with writing computer programs that can solve problems creatively; "workers in AI hope to imitate or duplicate intelligence in computers and robots" [syn: artificial intelligence]
3 a sloth that has three long claws on each forefoot [syn: three-toed sloth, Bradypus tridactylus]
4 the introduction of semen into the oviduct or uterus by some means other than sexual intercourse [syn: artificial insemination]

User Contributed Dictionary


AI, A.I.
  1. artificial intelligence
  2. action item
  3. (British airforce) airborne intelligence (syn. for an early type of airborne radar)
  4. artificial insemination
  5. reference to the computer opponent(s) and/or the specific behaviors coded into the game ("pathfinding AI" or "economic AI").
  6. articulatory index
  7. Air India
  8. artificial insemination.


artificial intelligence
  • French: IA
artificial insemination
  • French: IA


  • American Heritage 2000

Extensive Definition

Artificial intelligence (AI) is both the intelligence of machines and the branch of computer science which aims to create it.
Major AI textbooks define artificial intelligence as "the study and design of intelligent agents," where an intelligent agent is a system that perceives its environment and takes actions which maximize its chances of success. AI can be seen as a realization of an abstract intelligent agent (AIA) which exhibits the functional essence of intelligence. John McCarthy, who coined the term in 1956, defines it as "the science and engineering of making intelligent machines."
Among the traits that researchers hope machines will exhibit are reasoning, knowledge, planning, learning, communication, perception and the ability to move and manipulate objects. General intelligence (or "strong AI") has not yet been achieved and is a long-term goal of AI research.
AI research uses tools and insights from many fields, including computer science, psychology, philosophy, neuroscience, cognitive science, linguistics, ontology, operations research, economics, control theory, probability, optimization and logic. AI research also overlaps with tasks such as robotics, control systems, scheduling, data mining, logistics, speech recognition, facial recognition and many others. Other names for the field have been proposed, such as computational intelligence, synthetic intelligence, or computational rationality.

Perspectives on AI

AI in myth, fiction and speculation

Humanity has imagined in great detail the implications of thinking machines or artificial beings. They appear in Greek myths, such as Talos of Crete, the golden robots of Hephaestus and Pygmalion's Galatea. The earliest known humanoid robots (or automatons) were sacred statues worshipped in Egypt and Greece, believed to have been endowed with genuine consciousness by craftsman. In medieval times, alchemists such as Paracelsus claimed to have created artificial beings. Realistic clockwork imitations of human beings have been built by people such as Yan Shi, Hero of Alexandria, Al-Jazari and Wolfgang von Kempelen. Pamela McCorduck observes that "artificial intelligence in one form or another is an idea that has pervaded Western intellectual history, a dream in urgent need of being realized."
In modern fiction, beginning with Mary Shelley's classic Frankenstein, writers have explored the ethical issues presented by thinking machines. If a machine can be created that has intelligence, can it also feel? If it can feel, does it have the same rights as a human being? This is a key issue in Frankenstein as well as in modern science fiction: for example, the film Artificial Intelligence: A.I. considers a machine in the form of a small boy which has been given the ability to feel human emotions, including, tragically, the capacity to suffer. This issue is also being considered by futurists, such as California's Institute for the Future under the name "robot rights", although many critics believe that the discussion is premature.
Science fiction writers and futurists have also speculated on the technology's potential impact on humanity. In fiction, AI has appeared as a servant (R2D2), a comrade (Lt. Commander Data), an extension to human abilities (Ghost in the Shell), a conqueror (The Matrix), a dictator (With Folded Hands) and an exterminator (Terminator, Battlestar Galactica). Some realistic potential consequences of AI are decreased human labor demand, the enhancement of human ability or experience, and a need for redefinition of human identity and basic values.
Futurists estimate the capabilities of machines using Moore's Law, which measures the relentless exponential improvement in digital technology with uncanny accuracy. Ray Kurzweil has calculated that desktop computers will have the same processing power as human brains by the year 2029, and that by 2045 artificial intelligence will reach a point where it is able to improve itself at a rate that far exceeds anything conceivable in the past, a scenario that science fiction writer Vernor Vinge named the "technological singularity".
"Artificial intelligence is the next stage in evolution," Edward Fredkin said in the 1980s, expressing an idea first proposed by Samuel Butler's Darwin Among the Machines (1863), and expanded upon by George Dyson in his book of the same name (1998). Several futurists and science fiction writers have predicted that human beings and machines will merge in the future into cyborgs that are more capable and powerful than either. This idea, called transhumanism, has roots in Aldous Huxley and Robert Ettinger, is now associated with robot designer Hans Moravec, cyberneticist Kevin Warwick and Ray Kurzweil.
The field of modern AI research was founded at conference on the campus of Dartmouth College in the summer of 1956. Those who attended would become the leaders of AI research for many decades, especially John McCarthy, Marvin Minsky, Allen Newell and Herbert Simon, who founded AI laboratories at MIT, CMU and Stanford. They and their students wrote programs that were, to most people, simply astonishing: computers were solving word problems in algebra, proving logical theorems and speaking English. By the middle 60s their research was heavily funded by the U.S. Department of Defense and they were optimistic about the future of the new field:
  • 1965, H. A. Simon: "[M]achines will be capable, within twenty years, of doing any work a man can do"
  • 1967, Marvin Minsky: "Within a generation ... the problem of creating 'artificial intelligence' will substantially be solved."
These predictions, and many like them, would not come true. They had failed to recognize the difficulty of some of the problems they faced. In 1974, in response to the criticism of England's Sir James Lighthill and ongoing pressure from Congress to fund more productive projects, the U.S. and British governments cut off all undirected, exploratory research in AI. This was the first AI Winter.
In the early 80s, AI research was revived by the commercial success of expert systems (a form of AI program that simulated the knowledge and analytical skills of one or more human experts) and by 1985 the market for AI had reached more than a billion dollars. Minsky and others warned the community that enthusiasm for AI had spiraled out of control and that disappointment was sure to follow. Beginning with the collapse of the Lisp Machine market in 1987, AI once again fell into disrepute, and a second, more lasting AI Winter began.
In the 90s and early 21st century AI achieved its greatest successes, albeit somewhat behind the scenes. Artificial intelligence was adopted throughout the technology industry, providing the heavy lifting for logistics, data mining, medical diagnosis and many other areas. The success was due to several factors: the incredible power of computers today (see Moore's law), a greater emphasis on solving specific subproblems, the creation of new ties between AI and other fields working on similar problems, and above all a new commitment by researchers to solid mathematical methods and rigorous scientific standards.

Philosophy of AI

portalpar Mind and Brain
In a classic 1950 paper, Alan Turing posed the question "Can Machines Think?" In the years since, the philosophy of artificial intelligence has attempted to answer it.
  • Turing's "polite convention": If a machine acts as intelligently as a human being, then it is as intelligent as a human being. Alan Turing realized that, ultimately, we can only judge the intelligence of machine based on its behavior. This insight forms the basis of the Turing test.
  • The Dartmouth proposal: Every aspect of learning or any other feature of intelligence can be so precisely described that a machine can be made to simulate it. This assertion was printed in the proposal for the Dartmouth Conference of 1956, and represents the position of most working AI researchers.
  • Newell and Simon's physical symbol system hypothesis: A physical symbol system has the necessary and sufficient means of general intelligent action. This statement claims that the essence of intelligence is symbol manipulation. Hubert Dreyfus argued that, on the contrary, human expertise depends on unconscious instinct rather than conscious symbol manipulation and on having a "feel" for the situation rather than explicit symbolic knowledge.
  • Gödel's incompleteness theorem: A physical symbol system can not prove all true statements. Roger Penrose is among those who claim that Gödel's theorem limits what machines can do.
  • Searle's "strong AI position": A physical symbol system can have a mind and mental states. Searle counters this assertion with his Chinese room argument, which asks us to look inside the computer and try to find where the "mind" might be.
  • The artificial brain argument: The brain can be simulated. Hans Moravec, Ray Kurzweil and others have argued that it is technologically feasible to copy the brain directly into hardware and software, and that such a simulation will be essentially identical to the original. This argument combines the idea that a suitably powerful machine can simulate any process, with the materialist idea that the mind is the result of a physical process in the brain.

AI research

Problems of AI

While there is no universally accepted definition of intelligence, AI researchers have studied several traits that are considered essential. By the late 80s and 90s, AI research had also developed highly successful methods for dealing with uncertain or incomplete information, employing concepts from probability and economics.
For difficult problems, most of these algorithms can require enormous computational resources — most experience a "combinatorial explosion": the amount of memory or computer time required becomes astronomical when the problem goes beyond a certain size. The search for more efficient problem solving algorithms is a high priority for AI research.
It is not clear, however, that conscious human reasoning is any more efficient when faced with a difficult abstract problem. Cognitive scientists have demonstrated that human beings solve most of their problems using unconscious reasoning, rather than the conscious, step-by-step deduction that early AI research was able to model. Embodied cognitive science argues that unconscious sensorimotor skills are essential to our problem solving abilities. It is hoped that sub-symbolic methods, like computational intelligence and situated AI, will be able to model these instinctive skills. The problem of unconscious problem solving, which forms part of our commonsense reasoning, is largely unsolved.

Knowledge representation

Knowledge representation and knowledge engineering are central to AI research. Many of the problems machines are expected to solve will require extensive knowledge about the world. Among the things that AI needs to represent are: objects, properties, categories and relations between objects; situations, events, states and time; causes and effects; knowledge about knowledge (what we know about what other people know); and many other, less well researched domains. A complete representation of "what exists" is an ontology (borrowing a word from traditional philosophy), of which the most general are called upper ontologies.
Among the most difficult problems in knowledge representation are:
  • Default reasoning and the qualification problem: Many of the things people know take the form of "working assumptions." For example, if a bird comes up in conversation, people typically picture an animal that is fist sized, sings, and flies. None of these things are true about birds in general. John McCarthy identified this problem in 1969 as the qualification problem: for any commonsense rule that AI researchers care to represent, there tend to be a huge number of exceptions. Almost nothing is simply true or false in the way that abstract logic requires. AI research has explored a number of solutions to this problem.
  • Unconscious knowledge: Much of what people know isn't represented as "facts" or "statements" that they could actually say out loud. They take the form of intuitions or tendencies and are represented in the brain unconsciously and sub-symbolically. This unconscious knowledge informs, supports and provides a context for our conscious knowledge. As with the related problem of unconscious reasoning, it is hoped that situated AI or computational intelligence will provide ways to represent this kind of knowledge.
  • The breadth of common sense knowledge: The number of atomic facts that the average person knows is astronomical. Research projects that attempt to build a complete knowledge base of commonsense knowledge, such as Cyc, require enormous amounts of tedious step-by-step ontological engineering — they must be built, by hand, one complicated concept at a time.


Intelligent agents must be able to set goals and achieve them. They need a way to visualize the future: they must have a representation of the state of the world and be able to make predictions about how their actions will change it. They must also attempt to determine the utility or "value" of the choices available to it.
In some planning problems, the agent can assume that it is the only thing acting on the world and it can be certain what the consequences of its actions may be. However, if this is not true, it must periodically check if the world matches its predictions and it must change its plan as this becomes necessary, requiring the agent to reason under uncertainty.
Multi-agent planning tries to determine the best plan for a community of agents, using cooperation and competition to achieve a given goal. Emergent behavior such as this is used by both evolutionary algorithms and swarm intelligence.


Important machine learning problems are:
  • Unsupervised learning: find a model that matches a stream of input "experiences", and be able to predict what new "experiences" to expect.
  • Supervised learning, such as classification (be able to determine what category something belongs in, after seeing a number of examples of things from each category), or regression (given a set of numerical input/output examples, discover a continuous function that would generate the outputs from the inputs).
  • Reinforcement learning: the agent is rewarded for good responses and punished for bad ones. (These can be analyzed in terms decision theory, using concepts like utility).

Natural language processing

Natural language processing gives machines the ability to read and understand the languages human beings speak. Many researchers hope that a sufficiently powerful natural language processing system would be able to acquire knowledge on its own, by reading the existing text available over the internet. Some straightforward applications of natural language processing include information retrieval (or text mining) and machine translation.

Motion and manipulation

The field of robotics is closely related to AI. Intelligence is required for robots to be able to handle such tasks as object manipulation and navigation, with sub-problems of localization (knowing where you are), mapping (learning what is around you) and motion planning (figuring out how to get there).


Machine perception is the ability to use input from sensors (such as cameras, microphones, sonar and others more exotic) to deduce aspects of the world. Computer vision is the ability to analyze visual input. A few selected subproblems are speech recognition, facial recognition and object recognition.

Social intelligence

Emotion and social skills play two roles for an intelligent agent:
  • It must be able to predict the actions of others, by understanding their motives and emotional states. (This involves elements of game theory, decision theory, as well as the ability to model human emotions and the perceptual skills to detect emotions.)
  • For good human-computer interaction, an intelligent machine also needs to display emotions — at the very least it must appear polite and sensitive to the humans it interacts with. At best, it should appear to have normal emotions itself.


A sub-field of AI addresses creativity both theoretically (from a philosophical and psychological perspective) and practically (via specific implementations of systems that generate outputs that can be considered creative).

General intelligence

Most researchers hope that their work will eventually be incorporated into a machine with general intelligence (known as strong AI), combining all the skills above and exceeding human abilities at most or all of them.

Approaches to AI

There are as many approaches to AI as there are AI researchers—any coarse categorization is likely to be unfair to someone. Artificial intelligence communities have grown up around particular problems, institutions and researchers, as well as the theoretical insights that define the approaches described below. Artificial intelligence is a young science and is still a fragmented collection of subfields. At present, there is no established unifying theory that links the subfields into a coherent whole.

Cybernetics and brain simulation

In the 40s and 50s, a number of researchers explored the connection between neurology, information theory, and cybernetics. Some of them built machines that used electronic networks to exhibit rudimentary intelligence, such as W. Grey Walter's turtles and the Johns Hopkins Beast. Many of these researchers gathered for meetings of the Teleological Society at Princeton and the Ratio Club in England.

Traditional symbolic AI

When access to digital computers became possible in the middle 1950s, AI research began to explore the possibility that human intelligence could be reduced to symbol manipulation. The research was centered in three institutions: CMU, Stanford and MIT, and each one developed its own style of research. John Haugeland named these approaches to AI "good old fashioned AI" or "GOFAI".

Sub-symbolic AI

During the 1960s, symbolic approaches had achieved great success at simulating high-level thinking in small demonstration programs. Approaches based on cybernetics or neural networks were abandoned or pushed into the background. By the 1980s, however, progress in symbolic AI seemed to stall and many believed that symbolic systems would never be able to imitate all the processes of human cognition, especially perception, robotics, learning and pattern recognition. A number of researchers began to look into "sub-symbolic" approaches to specific AI problems.

Intelligent agent paradigm

The "intelligent agent" paradigm became widely accepted during the 1990s. Although earlier researchers had proposed modular "divide and conquer" approaches to AI, the intelligent agent did not reach its modern form until Judea Pearl, Alan Newell and others brought concepts from decision theory and economics into the study of AI. When the economist's definition of a rational agent was married to computer science's definition of an object or module, the intelligent agent paradigm was complete.
An intelligent agent is a system that perceives its environment and takes actions which maximizes its chances of success. The simplest intelligent agents are programs that solve specific problems. The most complicated intelligent agents would be rational, thinking human beings. A system with both symbolic and sub-symbolic components is a hybrid intelligent system, and the study of such systems is artificial intelligence systems integration. A hierarchical control system provides a bridge between sub-symbolic AI at its lowest, reactive levels and traditional symbolic AI at its highest levels, where relaxed time constraints permit planning and world modelling. Rodney Brooks' subsumption architecture was an early proposal for such a hierarchical system.

Tools of AI research

In the course of 50 years of research, AI has developed a large number of tools to solve the most difficult problems in computer science. A few of the most general of these methods are discussed below.


Many problems in AI can be solved in theory by intelligently searching through many possible solutions: Reasoning can be reduced to performing a search. For example, logical proof can be viewed as searching for a path that leads from premises to conclusions, where each step is the application of an inference rule. Planning algorithms search through trees of goals and subgoals, attempting to find a path to a target goal. Robotics algorithms for moving limbs and grasping objects use local searches in configuration space. Naive algorithms quickly run into problems when they expand the size of their search space to astronomical numbers. The result is a search that is too slow or never completes.


Logic was introduced into AI research by John McCarthy in his 1958 Advice Taker proposal. The most important technical development was J. Alan Robinson's discovery of the resolution and unification algorithm for logical deduction in 1963. This procedure is simple, complete and entirely algorithmic, and can easily be performed by digital computers. However, a naive implementation of the algorithm quickly leads to a combinatorial explosion or an infinite loop. In 1974, Robert Kowalski suggested representing logical expressions as Horn clauses (statements in the form of rules: "if p then q"), which reduced logical deduction to backward chaining or forward chaining. This greatly alleviated (but did not eliminate) the problem.
Logic is used for knowledge representation and problem solving, but it can be applied to other problems as well. For example, the satplan algorithm uses logic for planning, and inductive logic programming is a method for learning.
There are several different forms of logic used in AI research.
  • Fuzzy logic, a version of first-order logic which allows the truth of a statement to be represented as a value between 0 and 1, rather than simply True (1) or False (0). Fuzzy systems can be used for uncertain reasoning and have been widely used in modern industrial and consumer product control systems.
Bayesian networks are very general tool that can be used for a large number of problems: reasoning (using the Bayesian inference algorithm), learning (using the expectation-maximization algorithm), planning (using decision networks) and perception (using dynamic Bayesian networks).
Probabilistic algorithms can also be used for filtering, prediction, smoothing and finding explanations for streams of data, helping perception systems to analyze processes that occur over time (e.g., hidden Markov models and Kalman filters).
Planning problems have also taken advantages of other tools from economics, such as decision theory and decision analysis, information value theory, Markov decision processes, dynamic decision networks,

Classifiers and statistical learning methods

The simplest AI applications can be divided into two types: classifiers ("if shiny then diamond") and controllers ("if shiny then pick up"). Controllers do however also classify conditions before inferring actions, and therefore classification forms a central part of many AI systems.
Classifiers are functions that use pattern matching to determine a closest match. They can be tuned according to examples, making them very attractive for use in AI. These examples are known as observations or patterns. In supervised learning, each pattern belongs to a certain predefined class. A class can be seen as a decision that has to be made. All the observations combined with their class labels are known as a data set.
When a new observation is received, that observation is classified based on previous experience. A classifier can be trained in various ways; there are many statistical and machine learning approaches.
A wide range of classifiers are available, each with its strengths and weaknesses. Classifier performance depends greatly on the characteristics of the data to be classified. There is no single classifier that works best on all given problems; this is also referred to as the "no free lunch" theorem. Various empirical tests have been performed to compare classifier performance and to find the characteristics of data that determine classifier performance. Determining a suitable classifier for a given problem is however still more an art than science.
The most widely used classifiers are the neural network, k-nearest neighbor algorithm, Gaussian mixture model, naive Bayes classifier, and decision tree. The performance of these classifiers have been compared over a wide range of classification tasks in order to find data characteristics that determine classifier performance.

Neural networks

The study of artificial neural networksbegan with cybernetics researchers, working in the decade before the field AI research was founded. In the 1960s Frank Rosenblatt developed an important early version, the perceptron
Paul Werbos developed the backpropagation algorithm for multilayer perceptrons in 1974,which led to a renaissance in neural network research and connectionism in general in the middle 1980s. Other common network architectures which have been developed include the feedforward neural network, the radial basis network, the Kohonen self-organizing map and various recurrent neural networks. The Hopfield net, a form of attractor network, was first described by John Hopfield in 1982.
Neural networks are applied to the problem of learning, using such techniques as Hebbian learning and the relatively new field of Hierarchical Temporal Memory which simulates the architecture of the neocortex.

Social and emergent models

Several algorithms for learning use tools from evolutionary computation, such as genetic algorithms , swarm intelligence. and genetic programming.

Control theory

Control theory, the grandchild of cybernetics, has many important applications, especially in robotics.

Specialized languages

AI researchers have developed several specialized languages for AI research:

Competitions and prizes

There are a number of competitions and prizes to promote research in artificial intelligence. The main areas promoted are: general machine intelligence, conversational behaviour, data-mining, driverless cars, robot soccer and games.

Applications of artificial intelligence

Artificial intelligence has successfully been used in a wide range of fields including medical diagnosis, stock trading, robot control, law, scientific discovery and toys. Frequently, when a technique reaches mainstream use it is no longer considered artificial intelligence, sometimes described as the AI effect. It may also become integrated into artificial life.

See also



Major AI textbooks

  • Artificial Intelligence: Structures and Strategies for Complex Problem Solving">}}
  • Artificial Intelligence: A New Synthesis
  • Computational Intelligence: A Logical Approach

Other sources

  • ACM Computing Classification System: Artificial intelligence
  • Elephants Don't Play Chess
  • A (Very) Brief History of Artificial Intelligence
  • Artificial Intelligence: The Very Idea .
  • On Intelligence .
  • Judgment under uncertainty: Heuristics and biases .
  • The Age of Spiritual Machines
  • The Singularity is Near
  • Where Mathematics Comes From: How the Embodied Mind Brings Mathematics into Being .
  • Building Large Knowledge-Based Systems
  • Artificial Intelligence: a paper symposium
  • A Proposal for the Dartmouth Summer Research Project on Artificial Intelligence .
  • Some philosophical problems from the standpoint of artificial intelligence
  • Machines Who Think .
  • Computation: Finite and Infinite Machines
  • The Emotion Machine
  • The Role of Raw Power in Intelligence
  • Mind Children
  • Funding">
  • Computers and Thought
  • Minds, Brains and Programs
  • Encyclopedia of Artificial Intelligence .
  • The Shape of Automation for Men and Management
  • Computing machinery and intelligence
  • New horizons in psychology
  • Computer Power and Human Reason

Further reading

  • R. Sun & L. Bookman, (eds.), Computational Architectures: Integrating Neural and Symbolic Processes. Kluwer Academic Publishers, Needham, MA. 1994.
AI in Arabic: ذكاء اصطناعي
AI in Bengali: কৃত্রিম বুদ্ধিমত্তা
AI in Min Nan: Jîn-kang tì-hūi
AI in Bosnian: Vještačka inteligencija
AI in Bulgarian: Изкуствен интелект
AI in Catalan: Intel·ligència artificial
AI in Czech: Umělá inteligence
AI in Danish: Kunstig intelligens
AI in German: Künstliche Intelligenz
AI in Estonian: Tehisintellekt
AI in Modern Greek (1453-): Τεχνητή νοημοσύνη
AI in Spanish: Inteligencia artificial
AI in Esperanto: Artefarita inteligenteco
AI in Basque: Adimen artifizial
AI in Persian: هوش مصنوعی
AI in French: Intelligence artificielle
AI in Galician: Intelixencia artificial
AI in Korean: 인공지능
AI in Hindi: आर्टिफिशियल इंटेलिजेंस
AI in Croatian: Umjetna inteligencija
AI in Ido: Artifical inteligenteso
AI in Indonesian: Kecerdasan buatan
AI in Interlingua (International Auxiliary Language Association): Intelligentia artificial
AI in Icelandic: Gervigreind
AI in Italian: Intelligenza artificiale
AI in Hebrew: בינה מלאכותית
AI in Latvian: Mākslīgais intelekts
AI in Lithuanian: Dirbtinis intelektas
AI in Lojban: rutni menli
AI in Hungarian: Mesterséges intelligencia
AI in Marathi: कृत्रिम बुद्धिमत्ता
AI in Malay (macrolanguage): Kecerdasan buatan
AI in Dutch: Kunstmatige intelligentie
AI in Japanese: 人工知能
AI in Norwegian: Kunstig intelligens
AI in Norwegian Nynorsk: Kunstig intelligens
AI in Polish: Sztuczna inteligencja
AI in Portuguese: Inteligência artificial
AI in Kölsch: Artificial Intelligence
AI in Romanian: Inteligenţă artificială
AI in Russian: Искусственный интеллект
AI in Simple English: Artificial intelligence
AI in Slovak: Umelá inteligencia
AI in Slovenian: Umetna inteligenca
AI in Serbian: Вјештачка интелигенција
AI in Serbo-Croatian: Umjetna inteligencija
AI in Finnish: Tekoäly
AI in Swedish: Artificiell intelligens
AI in Thai: ปัญญาประดิษฐ์
AI in Vietnamese: Trí tuệ nhân tạo
AI in Turkish: Yapay zekâ
AI in Turkmen: Ýasama akyl
AI in Ukrainian: Штучний інтелект
AI in Chinese: 人工智能
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