Famous Expert Systems

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Famous Expert Systems
Before expert systems ("in the beginning...")
Detailed Operation Procedures (DOP's) used by
aeronautics industry and NASA, they are expert
knowledge codified in written form. -
Not implemented on a computer. However, using a
DOP is like manually following an
algorithm by hand
(ignizio p.49) Heuristic
programming use heuristics to solve large,
complex computational problems (early
1960's) - Controversy whether expert
systems are just examples of heuristic
programming
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1. DENDRAL
First expert system Project began at
Stanford in mid 1960's, and is still being
used. Domain Organic chemistry - mass
spectrometry Task identify molecular
structure of unknown compounds from mass
spectra data Input Histogram giving mass
number/intensity pairs Output Description of
structure of the compound Architecture
plan-generate-test with constrained heuristic
search Tools production rules implemented
in Lisp Results "Discovery" of knowledge
engineering. Many published
results.
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DENDRAL
Winston
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DENDRAL
Winston
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DENDRAL
Winston p. 200
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DENDRAL
Procedure 1. Spectra data given as input 2.
Preliminary analysis determines -
necessary compounds -- spectra data -
forbidden compounds -- spectra data, expert
knowledge 3. Generate and test a)
structure enumerator can generate all possible
compounds - Takes necessary and
forbidden lists, and creates a new possible
compound - output is formula
b) spectra synthesizer generates spectra
data for this compound c) matcher - matches
synthesized spectra with actual one -
compound with best fit is the one Note all
compounds checked. Complexity reduced because of
the pruning done in step 2
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DENDRAL
Example rule for analyzer
Winston 201
Matcher is involved needs expert knowledge
in knowing when some peaks are more important
than others
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2. MACSYMA
Developed at MIT since 1968 onwards
Domain high-performance symbolic math (algebra,
calculus, differential equations,...)
Task carry out complex mathematical
derivations Input formulae and commands
(interactive) Output Solutions to tough
problems Method Brute force (expert
techniques are encoded as algorithm)
Architecture programmed in Lisp (300,000 lines
of code) Results Widely used, powerful
system. Newest version Maxima -
Free! Open source. - works on Windows, linux,
MacOS - maxima.sourceforge.net
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MACSYMA
p.136-7 Harmon
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3. Hearsay I and II
Developed at Carnegie-Mellon in late 1960's
Domain speech understanding for simple
database query Task Using specific
vocabulary and grammar criteria, generate
correct speech recognition Input Speech
wave Output Ordered list of hypotheses of
what was said, plus database query based on
best guess Architecture Opportunistic,
agenda-based reasoning, using "blackboard" to
record hypotheses from multiple independent
knowledge sources (Definition Blackboard
common working memory for independent systems)
Tools Programmed in SAIL
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HEARSAY
Results - proved feasibility of
automated speech recognition - pioneering
effort in system architecture techniques
- blackboard for multiple
knowledge sources - power of
symbolic computation over purely statistical
ones - Spawned other expert system projects.
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HEARSAY
Harmon 138
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HEARSAY
Harmon 139
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4. INTERNIST/CADUCEUS
Developed at U of Pittsburgh in early 1970's
thru mid 80s Domain diagnostic aid for all
of internal medicine Task medical diagnosis
given interactive input Input Answers to
interactive queries Output ordered set of
diagnoses Architecture forward chaining
with "scores" for diseases Tools programmed
in Lisp Results ambitious project
inspired other systems
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INTERNIST
p.141-144 Harmon
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INTERNIST
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5. MYCIN
Stanford U in mid 70's Domain Medical
diagnosis for bacterial and meningitis
infections Task interview physician, make
diagnosis and therapy recommendations Input
Answers to queries Output Ordered set of
diagnoses and therapies Architecture
rule-based exhaustive backward chaining with
uncertainty Tools programmed in LISP (shell
called EMYCIN -- empty MYCIN) Results not
in general use, but was ground-breaking work in
diagnostic consultation systems Made
acceptable diagnoses at a rate of 69 (better
than human experts!)
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MYCIN
p.16-20 Harmon
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6. Prospector
Developed at SRI international in late
1970's Domain exploratory geology Task
evaluate geological sites Input geological
survey data Output maps and site
evaluations Architecture rule-like semantic
net with uncertainty Tools programmed in
LISP, and is a descendant of MYCIN Results
In one blind test, the program identified a
previously undiscovered site, thus showing
commercial viability of expert systems.
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PROSPECTOR
p. 146 Harmon
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PROSPECTOR
p. 145 Harmon
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7. PUFF
Developed at Stanford in 1979 Domain
Diagnosis of obstructive airway diseases using
MYCIN's inference engine and a new knowledge
base Task Take data from instruments and
dialog, and diagnose type and severity of
disease Input instruments, queries
Output Written report for physician to review
and annotate Architecture rule-based,
exhaustive backward chaining with
uncertainty Tools EMYCIN (Empty MYCIN)
Results Reports correct 86 of the time. A
55-rule system is in daily use, running in
Basic!
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PUFF
p.150 Harmon
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PUFF
p. 151 Harmon
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8. XCON (R1)
Originally called R1, developed at Carnegie
Mellon and DEC in late 70's Domain
configure computer hardware Task configure
VAX systems by projecting the need for
subassemblies given a high-level description
of the system Input Vax system
description Output list of parts,
accessories, and a plan for assembly
Architecture forward-chained, rule-based, with
almost no backtracking Tools OPS5, a
production system tool Results Used by DEC
and performed better than previous experts (since
fired) - by 1986, processed total of 80,000
orders with 95-98 accuracy - saved DEC 25
million a year
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XCON
p. 156 Harmon
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XCON
as of 1991, XCON has 8000 (!) production
rules a serious problem has developed
maintenance has been said that XCON replaced
75 experts with 150 XCON maintainers shows
the need for developing better maintenance
systems for large expert systems (and other
large software systems)
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Some other famous systems
DELTA/CATS - diagnose and repair diesel
locomotives - developed in LISP, but ported
to FORTRAN (a common phenomenon) DRILLING
ADVISOR - diagnose oil drilling problems
- rule-based, exhaustive backward chaining
with uncertainty, frames GENESIS -
designs molecular genetics experiments and
procedures - was used by over 500 research
scientists GATES - airline gate
assignment and tracking system - used by TWA
at JFK airport - implemented in Prolog on
microcomputers - access database for 100 daily
flights, and creates gate assignment in 30
seconds (experts took between 10 and 15
hours, with 1 hour per modification)
( possible extension lost luggage!)
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Conclusion
p. 170 Harmon
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A typical industrial system

• (Byte, Oct 1994) Picker International
• Problem domain
• Picker produce sophisticated medical diagnostic
  machines
• needed a system for use by their service
  technicians
• tasks
• intelligent service expert system full
  explanation, graphical UI, hypertext user manual
• onsite access to main service DB of user site
  data
• capture site data feedback for knowledge base
  improvements
• use site data to improve products, service
  effectiveness in future

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System

• Built with Carnegie Groups TestBuilder system
• shell system geared towards diagnostic systems
• systems are typically hierarchical, rule-based,
  object-oriented (frames)
• multi-level explanation important
• rule-level how, why
• deeper level hypertext manuals (interactive,
  graphical)
• TestBuilder is interactive KB editor and tester
• Final system is compiled into DOS executable form
• TestView is run-time system
• Compared with general-purpose shells, this system
  is specialized
• inference focusses on problem right away, via
  menus or natural language input
• completeness sacrificed for efficient focus on
  possible problem

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Conclusions from Pickers system

• Incremental design of system
• get prototype running on initial problems
• build onto it
• Can help if Knowledge engineer has domain
  knowledge
• caveat here, KE is already computer-oriented
• caveat problem domain well-adapted to
  Testbuilder paradigm
• On-site capture of new data permits continual
  update of system for free
• empirical data capture and DB useful for KB, as
  well as products themselves
• integrated standalone systems (eg. laptops) very
  handy!
• CD ROMs also can prevent need to download data