Knowledge-Based Expert Systems 2

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1-0 Knowledge-Based Expert U"! Systems A computer program which, with its associated data, embodies organised knowledge concerning some specific area of human activity. Such a system is expected to perform competently, skilfully and in a cost-effective manner; it may be thought of as a computer program which mimics the performance of a human expert. 

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1-0 Knowledge-Based Expert U"! Systems The Nature of Expertise One view of human expertise is that some people have spent so much time solving problems in one particular domain that they ‘know all there is to know’ (nearly) and are able to see any problem as an instance of a class of problems with which they have been confronted before. Once the expert has successfully classified or recognised a new problem as an instance ofa previously experienced problem type, all the expert has to do is apply whatever solution proved successful in dealing with that type of problem in the past. 

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1-0 Knowledge-Based Expert U"! Systems The Nature of Expertise This model of human expertise that relies (a) on domain-specific knowledge and (b) experience- based recognition of solutions of problems and has served as the basis of numerous expert systems. The idea is that cognition is a ‘recognition’- based phenomenon. That is, when a medical doctor, say, examines a patient or hears what the patient has to say about his or her problem, the configuration of symptoms or signs suggests a particular illness with which the doctor is already completely familiar. 

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Knowledge-Based Expert U"! Systems The Nature of Expertise The ‘recognition-based’ phenomenon can be viewed as setting up a key goal in the problem solving process and then attempting to find out data that satisfies the goal. The goal is then broken up into sub-goals and data sought to prove each of the sub-goals. (The sub-goals can be broken into further sub-goals and so on and on). While proving a sub-goal, the experts suspend the goal and try and satisfy individual goals. Once all sub-goals are satisfied then the key goal is deemed to be satisfied and the problem solved! 4 

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1-0 Knowledge-Based Expert U"! Systems Pneumonia Expert System Consider a small chunk of a medical experts knowledge about diagnosing pneumonia and fever rule pneumonia if ‘the patient has chest pain’ & ‘the patient has a fever’ & ‘the patient produces purulent sputum’ then ‘the patient has pneumonia’ rule fever if ‘the patient has a temperature above 100’ then ‘the patient has a fever’. The nurse has just come in a with a patient with the following symptoms: ‘the patient has a chest pain’ & ‘the patient has a temperature above 100’& ‘the patient produces purulent sputum’ And the expert has to deduce whether or not the patient has pneumonia? 

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1-0 Knowledge-Based Expert U"! Systems Pneumonia Expert System The nurse has just come ina with a patient with the following symptoms: ‘the patient has a chest pain’ & ‘the patient has a temperature above 100’& “the patient produces purulent sputum’ And. has to deduc whether or not the patient has pneumonia? In order to prove whether or not the patient has pneumonia, the expert has to prove: prove ‘the patient has pneumonia’ «GOAL prove ‘the patient has a chest pain’ ~ SUB-GOAL prove ‘the patient has a fever’ -SUB-GOAL prove ‘the patient produces purulent sputum’ <— SUB- GOAL 

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1-0 Knowledge-Based Expert U"! Systems #intelligent beings perceive, reason and act. 11161110612 beings are creative, learn from their mistakes. #intelligent beings can learn from their environment. @iIntelligent beings can learn with the help of tutors. @Intelligent beings can work on their own/form groups. @iIntelligent beings have a value system, an exchange system. 

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1-0 Knowledge-Based Expert U"! Systems MYCIN, microbial infection therapy system comprised over 400 rules of thumb such as below which help in microbial infection therapy, for example in the diagnosis and therapy of meningitis. IE: 1) The stain of the organism is grampos, and 2) The morphology of the organism is coccus, and 3) The growth conformation of the organism is chains THEN: There is suggestive evidence (0.7) that the identity of the organism is streptococcus. Each of the antecedent clauses and the consequent clause is essentially a complex relationship between the terms of this subject: the stain, morphology and growth, conformation of an organism and its identity and the attributes of these = grampos, coccus, chains, streptococcus. The rules show the interrelationship between various domain objects (‘the stain’ etc.) and how such a relationship could be used to infer new facts. The objects and their attributes, (for example, HaaArnhalany" and ite attmhiuta “"acarcic'\iu1noweon haro acia Aata 

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1-0 Knowledge-Based Expert U"! Systems The expert system R1/XCON was used by DEC(now a part of COMPAQ) for configuring computer systems. This system was in routine commercial use and contains over 10,000 rules of the type shown below IF: The most current active context is assigning a power supply & an sbi module of any type has been put in a cabinet & the position it occupies in the cabinet (its nexus) is known & there is space available in the cabinet for a power supply for that nexus & there is an available power supply THEN: _ put the power supply in the cabinet in the available space. The above rule is much more complex than the rule shown for MYCIN in that although we are talking about putting the power supply ig the cabinet in the available space, each of the domain objects and its 

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Knowledge-Based ExpertU" Environm ent Patient, hospital Images from orbiting satellite Conveyor belt with parts Refinery 10 Inputs | Actions | Goals Symptoms, | Questions, | Healthy findings, tests, patient, patient's _| treatment | minimise answers 5 costs Pixels of Print a Correct varying categorisa | categorisa intensity, _ | tion of tion colour scene Pixels of Pickup __| Place varying parts and_| parts in intensity sort into | correct bins 1 Temperatur | Open, e, pressure | close readings __| valves; Knowledge -Based Systems Medical diagnosis system Satellite image analysis system Part- picking robots Refinery controller 

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Knowledge-Based ExpertU"'S Systems A conventional computing USER INTERFACE ~~ ALGORITHM(S) Data DATA BASE COMPUTER SYSTEM 

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1-0 Knowledge-Based ExpertU"'S Systems A Knowledge-Based system USER INTERFACE HEURISTICS&ALGORITHM(S KNOWLEDGE BAS Data# Rules Meta Rules Facts COMPUTER SYSTEM 

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Uni Knowledge Base n organised and structured repository of ‘human knowledge’ in a given specialist domain. This repository can be updated or deleted in parts. Usually the knowledge is encoded as conditional ‘if <antecedent> then <consequent>‘ statements (‘rules’ and ‘problem-solving tasks’) together with the so-called ‘domain objects’. The latter are descriptions of facts, including concrete and abstract facts, relating to the specialist domain. 

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Uni Knowledge Base owledge representation is about making things explicit, is about resolving ambiguities; Knowledge representation, in the context of artificial intelligence, is about describing a class of things to a computer system. This description should not be ambiguous either lexically or structurally This description should explicate shared knowledge 

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ونم ‎Reasoning Strategies‏ 2 easoning may be characterised aS an attempt to combine elements of old information to form new information. Reasoning strategies refer to the rather long sequences of individual small inferences organised so as to address a main goal or problem. @Reasoning strategies involve the representation of information and knowledge, the use of inference rules for manipulating that knowledge & information, and control mechanisms for making the variety of choices necessary in the search for solutions. 15 

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Unis Problem Solving @Problem-solving is sometimes defined as a process that involves finding or constructing a solution to a problem. >Human problem solving can be modelled as the exploration of different paths to a solution and involves ‘information processing’ which appears unique to human beings. Cognitive psychologists typically divide problems into two classes: ‘well defined’ or closed world problems including solutions of games or puzzles and ‘ill defined’ or open world problems. 16 

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UniS Heuristics or Rules of thumb Prevent the hi-jacking of ۱ inli Prevent hi-jackers from boarding 1 the airliners Heuristic Algorithmic 1 technique —_ route luggage through a metal (inc. passengers, detector & flight crews & *Search only those who mechanics) set off the detector * Search those passengers that match a predetermined hi-jacker + profile *Search all luggage *Strip search every person with access to the airlines & 

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Uni Knowledge Based Systems & ,____Conventional Systems Conventio KBES nal Representa | &4@9T@2™S_— knowledge tien. Reasoning | algorithmi | heuristic & c& inferential Retrieves large DB large KB Knowledge | encrypted | represented 18 

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1-0 Knowledge Based Systems ‏لها‎ ‎Applications *There are recognised experts *The experts are provably better than novices *The tasks takes an expert a few minutes to a few hours (if it takes days - FORGET IT) *The task is primarily cognitive *The skill is routinely taught to novices *The task requires no common sense 5 

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ونم ‎Knowledge Engineering‏ The accumulation, codification and application of knowledge through the use of computer systems, specifically knowledge- based systems. 

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Uni$ 21 Knowledge Engineering The Good News Human Artificial Expertise Expertise Durability Perishable Permanent ‘Transfer Difficult. Easy Documentation _| Difficult Easy Consistency Unpredictable __|Consistent Cost. High Affordable The Bad News Human |Artificial [Expertise [Expertise (Creativity Yes [None [Adaptivity Yes [Limited ‏لاو‎ Sensory/ Symbolic only Symbolic Focus [Broad Narrow, (Common-sense_|Y es |None 

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22 Rule-based Systems @A rule-based system helps us to codify the problem-solving knowledge of the human expert. it appears that experts typically express their knowledge as a set of situation-action rules. RBS research should address the need to capture, represent, store, distribute, reason about and apply human knowledge electronically. Hayes Roth, F. (1992). ‘Rule-Based Systems’ p.1426 

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Uni Information Exchange & Natural Language Natural Language. A person’s native tongue. Natural Language interface. A system for communicating with a computer by using a natural language. Natural Language Processing. Processing of natural language (e.g., English) by a computer to facilitate communication with the computer or for other purposes, such as language translation. 23 

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1-0 Information Exchange andU"'S Visual I/O Recognising and reasoning about the visual environment something that people do extraordinarily well; In these abilities an average three year old makes the most sophisticated computer vision system look embarrassingly inept 

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Information Exchange andUniS Visual 1/0 Tke Osive Qvblew? Three-dimensional physical structure in the scene, containing pictures of objects related to other (probably) known objects, which projects into two dimensional structure in the image. 

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Representation: ‏5ن‎ ‎Production Systems *Production Systems are a modular knowledge representation scheme and are based on the notion of condition- action pairs, called production rules or just productions: "If this condition occurs, then do this action". *The utility of the production system formalism comes from the fact that the conditions in which each rule is applicable are made explicit and, in theory at least, the interactions between rules _are-minimised_in_the sense that the 

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Uni$ 27 Representation: Production Systems Consider a knowledge-base containing the THEN THEN THEN THEN THEN THEN following rules: A&B&C D&F A&J B IF IF IF IF IF IF Rule#1: D Rule#2: G Rule#3: G Rule#4: Cc Rule#5: B Rule#6: J 

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Representation: ‏5ن‎ ‎_ Production Systems 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? 1. EYP goal : is H 2.2 |Check H is not in the database Database 3 Find Rule 7 has H as an ‘appropriate |implication rule’ 4. |Fire rule 7 To prove that G is true 5. Set G as the Store this information in current goal | the Working Memory (WM) i arla thrnwunkh 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? 1. urrent goa : isG 2. |Check G is not in the database Database 3 | Find 1 Rule 2 has G as an appropriate | implication rule' 4. | Fire rule 2 To prove that D & F are true 5. |Set D as the Store D (<-( G<- H) inso ‏و تا و و‎ | aaa T. ‏وك تون روتكد كسد ار لس ات‎ 

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Uni$ 31 Representation: Production Systems Consider a knowledge-base containing the THEN THEN THEN THEN THEN THEN following rules: A&B&C D&F A&J B IF IF IF IF IF IF Rule#1: D Rule#2: G Rule#3: G Rule#4: Cc Rule#5: B Rule#6: J 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? 1. CUE goal . is D 2.2 |Check D is not in the database Database 3 Find Rule 1 has D as an ‘appropriate |implication rule’ 4. |) Fire rule 1 To prove that A&B&C are true 5. Set A as the Store A in the WM & B&C current goal are to be proven later on 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? ۲ Ces oF Proguction: FOURTH CYCLE) 1. ‘urrent goa isA 2. |Check Ais in the database Database 3 Set B as the Store B in the WM current goal 4 |Cycle through the KB 33 

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Uni$ 34 Representation: Production Systems Consider a knowledge-base containing the THEN THEN THEN THEN THEN THEN following rules: A&B&C D&F A&J B IF IF IF IF IF IF Rule#1: D Rule#2: G Rule#3: G Rule#4: Cc Rule#5: B Rule#6: J 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? 1. 229 goal isB 2. |Check B is not in the database Database 3 Find Rule 5 has B as an ‘appropriate [implication rule’ 4. Fire rule 5 To prove that F is true, hence B is true 5. Set C as the Store C in the WM 4 current goal 

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Representation: ‏5ن‎ ‎Production Systems An Example Problem: To prove that H is true? 1. 209 goal : isB 2. |Check C is not in the database Database 3 Fire rule 4 To prove that B is true, hence C is true 4. Goal D is Hence goal G, and therefore satisfied goal H is satisfied 5. |ISTOP 36 

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Representation: ‏5ن‎ ‎Production Systems Conflict Resolution ule Ordering range rules in list with most important rules higher up the list. Fire rules according to their position in list (highest first). ontext Limiting lace rules in groups, and only have one group ‘active’ at any one time. Specificity The specificity principle states that if a number of rules are applicable to a given situation then the rule with the greatest number of condition premises (I.e. the most specific) should be selected to fire. 37 

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Representation: ‏5ن‎ ‎Production Systems Conflict Resolution Refractoriness Refractoriness is another conflict resolution strategy which states that if a rule has been applied on a previous cycle, then it should not be applied again to the same set of facts in data memories. This kind of strategy prevents a system from getting itself entwined in a loop. Recency The recency principle is a conflict resolution strategy which states that if more than one rule applies to a given situation, then choose the rule that applies to the most recently entered items in data memory. 38 

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Deduction KBS Problem: Elicit rules from the following description Johnny is an amateur zookeeper and also keeps notes in his diary on the various animals and birds he comes in contact with, His diary contains the following entries: ‘Jan 1, 1992: Mary told me that meat-eating animals with pointed teeth, forward pointing eyes and claws are called carnivores. Like other mammals they give milk." ‘Feb. 15, 1992: I saw two tawny coloured carnivores today, but one had dark spots and the other black stripes. The dark spotted carnivore was called cheetah and the black striped was a tiger.’ ‘March 20, 1992: We had two new animals delivered to the zoo, a zebra and a giraffe. These hoofed mammals are called ungulates. The zebra has white skin with black stripes on it. The giraffe had long legs and neck, and has the same tawny colour as the tiger but with black|spots'; 

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Uni$ Deduction KBS Antecedenls Consequent 

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Uni$ Deduction KBS Johnny has been asked to identify a hoofed, long-necked hairy animal, Freddy, which has a tawny colour and dark spots. Use the forward chaining search strategy to draw the ce network which Johnny should use to identify the unknown animal, Gives milk{ —| Isamammal Fired 2nd Has hoofs 

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Uni$ Deduction KBS