Pragmatic Knowledge Acquisition 6.871 - Lecture 12Outline • The intent of this lecture • The longstanding dream • What do we mean “learn”? • What this lecture is not about • The nature of the task • Predictable difficulties • Pragmatics of debriefing 6.871 - Lecture 12 2The Dream: Version 1 COMPACTDISC 6.871 - Lecture 12 Figure by MIT OCW. 3The Dream: Version 2 6.871 - Lecture 12 Figure by MIT OCW. 4Modes of Learning • Learning by being programmed • Learning by being told • Learning from selected examples • Learning from unselected examples • Learning by discovery 6.871 - Lecture 12 5Learning by Being Programmed 00 00 00 . 2 6.871 - Lecture 12 6What This Lecture Is Not About • The variety of machine learning techniques: – PAC learning – Neural nets –ID-3 – Genetic algorithms – Nearest neighbor – Knowledge discovery and data mining –… 6.871 - Lecture 12 7What This Lecture Is Not About • The variety of cognitive science oriented techniques: – Multi-dimensional scaling – Personal construct theory – Ordered Trees from Recall –… 6.871 - Lecture 12 8A Key Hard Problem CREDIT (BLAME) ASSIGNMENT 6.871 - Lecture 12 9Pragmatic Techniques • Interviews • Observe (Record) Performance • Protocol Analysis 6.871 - Lecture 12 10Basic Interaction KNOWLEDGE ENGINEER SYSTEM EXPERT Listen Understand Reformulate Explain 6.871 - Lecture 12 11The Nature of the Task KNOWLEDGE Knowledge Engineering KNOWLEDGE REPRESENTATIONS Rules Procedures Logic Frames Semantic Nets 6.871 - Lecture 12 12Nature Of The Task • Bridging the gap • Building a formal a language – “sentences,” “nouns,” “verbs,” … – rules, attributes, objects, values • Working from both directions – kinds of knowledge – kinds of reps 6.871 - Lecture 12 13Predictable Difficulties • The expert… – … knows more than he says – … says more than he knows – … lies to you – … disagrees with other experts 6.871 - Lecture 12 14Predictable Difficulties • Knowledge engineers… – … rush to structure – … need social skills – … need AI skills 6.871 - Lecture 12 15Getting The Knowledge: Sources • Books • People – Finding one – Finding one • Level of aspiration – Finding the one • Confident • Introspective & Reductionistic • Intrigued 6.871 - Lecture 12 16What Representation to Use? • Medical diagnosis • Getting out of the supermarket 6.871 - Lecture 12 17What Representation to Use? • Medical diagnosis • Getting out of the supermarket ASK YOURSELF: WHAT DO YOU KNOW? Then listen to the answer. 6.871 - Lecture 12 18Getting The Knowledge: Debriefing • Signing on • Work from examples – dead center cases – marginal cases • Errors are wonderful – it’s easier to modify than specify • The relevance of the computer – mental hygiene – efficiency 6.871 - Lecture 12 19Getting The Knowledge: Debriefing • Be rabidly rational and reductionistic • Be patient • Get interested 6.871 - Lecture 12 20Getting The Knowledge: Debriefing • Meet the expert half way: – learn the expert’s language • Talk your language – it will be infectious • Come at hard problems from several directions 6.871 - Lecture 12 21Knowledge Acquisition:Getting Started • Determine the size and structure of the solution space – How many categories of answers are there? – How many specific choices within each category? • Select a category, select a specific choice • What factors suggest that choice as the correct one? • What factors differentiate among choices in that category? 6.871 - Lecture 12 22Knowledge Acquisition:Getting Started • Notice the vocabulary in use: – What are attributes, objects and values? • Notice statements like – “if X and Y, then the best choice is Z” • Look for chains of reasoning 6.871 - Lecture 12 23Example: Selecting an Investment • Frank’s Financial Supermarket offers 7 kinds of investments – stocks, index funds, bonds, commodities, mutual funds, rare coins, tax shelters • There are – 1500 stocks – 1000 bonds – 15 different mutual funds • In the mutual funds: – consider the tax-free money market fund 6.871 - Lecture 12 24Example: Selecting an Investment • What factors suggest that choice as the correct one? “If your tax bracket is 42% or higher and you need to keep the money readily at hand, then the tax-free mm fund is a good choice.” 6.871 - Lecture 12 25Example: Selecting an Investment • Notice the vocabulary in use “If your tax bracket is 42% or higher and you need to keep the money readily at hand, then the tax-free mm fund is a good choice.” • Look for chains of reasoning 6.871 - Lecture 12 26Example: Selecting an Investment • What factors differentiate among choices in that category? Why the tax free mm fund instead of the tax free bond fund? 6.871 - Lecture 12