A common ground theory
of medical decision-making
2: The knowledge ladder
John Fox
Department of Engineering Science
University of Oxford and OpenClinical
Knowledge based systems and
theories of knowledge
• Expert systems
– “a piece of software which uses databases of expert knowledge to
offer advice or make decisions in such areas as medical diagnosis”
• Knowledge based systems
– “A KBS is a computer program that reasons and uses knowledge to
solve complex problems”
• Knowledge representation
– “use of symbols … in a conceptual model of the world; symbols
are arranged in order to form semantic constructions and express
relations between concepts”
Knowledge engineering
• Representation and formalisation of knowledge
– Domain specific and general knowledge
– Theory and semantics of concepts and ontologies
• Knowledge acquisition
– Elicitation of knowledge from human experts
– Semi-automatic methods (e.g. machine learning)
• Symbolic processing techniques
– Computational architectures for knowledge processing
– Practical tools for creating and maintaining knowledge
bases
PROforma: A knowledge representation
language for decision engineering
• A general notation for modelling
clinical processes
• Grounded in a logical theory of
decisions, plans and knowledge
• Applications are composed out of
a minimal set of generalised task
models
Fox et al, Proc. MIE 1996;
Fox and Das, MIT Press, 2000
Sutton and Fox JAMIA, 2003
An analogy
from music
OpenClinical.net: a repertoire of
medical compositions
Formalising and sharing knowledge
Source content
Trials, systematic reviews,
guidelines,
evidence
Point of care
e.g. Routine care,
clinical research,
patient services
Machine executable
models of practice
PROforma+
Open access, open
source repository
Repertoire
The CREDO
stack
The medical knowledge ladder
Agents
Plans
Decisions
Rules
Descriptions
Concepts
Terms
WHO International classification of diseases
Primary
healthcare
Information
Support
Other
healthcare
related
classifications
Terms
3-character core
Speciality codes
• Diagnoses
• Symptoms
• Abnormal Lab
findings
• Injuries and
poisonings
• External causes of
morbidity and
mortality
• Factors influencing
health status
• oncology
• dentistry
• dermatology
• psychology
• neurology
• obstetrics & gynaecology
• rheumatology &
orthopaedics
• general medical practice
International
Nomenclature
of Diseases
SNOMED
Systematized NOmenclature of MEDicine
• A general purpose, comprehensive medical
terminology
• Computer-readable standard
• Representing and indexing “virtually all of the
events found in the medical record”
• SNOMED CT (Clinical Terms) is being widely
promoted as a global language (English)
Concepts
• Formalisms for organising and
formalising the meaning of concepts
in a domain
• Domain concepts linked together in a
network using relations characteristic
of the domain
• Class hierarchies
– Inheritance of attributes over classes
Concepts
Terms
Ontologies and descriptions
• Capture common understanding of the
meaning of information
– Between people, computers, both
• Enable sound techniques for reasoning,
decision-making, planning, learning … by
computers
• Introduce standards across medical specialties
• Enable trustworthy use and reuse of domain
knowledge
Ontologies and descriptions
(compare semantic networks, dependency graphs, BNs)
Patient1
Patient2
Symptoms
IS_A
Lump
causes
instance
instance
IS_A
Chemotherapy
IS_A
Radiotherapy
Weight loss
IS_A
Descriptions
Breast cancer
Treatments
caused_by
Concepts
Terms
IS_A
Cancer
Rule-based decision support
Rules
Descriptions
Concepts
Terms
if last_creatinine is not present then
alert_text := "No recent creatinine available. Consider
ordering creatinine before giving IV contrast.";
conclude true;
elseif last_creatinine > 1.5 then
alert_text := ”This patient has an elevated creatinine.
Giving IV contrast may worsen renal function." ;
conclude true;
else conclude false;
endif;
Reasoning over ontologies
if Subclass is a kind of Class and
Property is a property of Class
then Property is a property of SubClass
If Disease is a cause of Symptom and
Patient has Symptom
then possible diagnosis of Symptom in Patient is
Disease
Description logics
• Descriptions of medical facts and clinical data
stated in propositional sentences in some L
• First order predicate calculus is a commonly used
and versatile/powerful tool for reasoning over
ontologies and descriptions
• Known to be computationally intractable in worst
case
– do not need all the power of FOPC;
– adopt simpler axioms with more favourable
computational properties
– http://en.wikipedia.org/wiki/Description_Logics
PROforma “task” ontology
Terms to descriptions
Descriptions
Concepts
Terms
Rules in PROforma
Rules
Descriptions
Concepts
Terms
PROforma decision engineering
Decisions
Rules
Descriptions
Concepts
Terms
PROforma decision model
Decisions
Rules
Descriptions
Concepts
Terms
Decisions in context:
workflows, care plans and pathways
Plans
Decisions
Rules
Descriptions
Concepts
Terms
Kinds of decision-making and expertise
Agents
Plans
Decisions
Rules
Descriptions
Concepts
Terms
https://en.wikipedia.org/wiki/Expert_system
Conclusions
• Understanding medical expertise requires general models for
reasoning, decision-making, planning etc (of course)
• … but a key (the largest?) component of medical expertise is
what the expert knows
• AI and knowledge representation research have shown that
knowledge is semantically complex but systematically
structured
• Theories of knowledge and techniques of knowledge
engineering open up exciting possibilities for formalising and
sharing medical expertise and exploring new techniques for
improving decision-making and the quality and safety of
common medical practice
Conversations are two way…
• OpenClinical.net is based on a kind of
publishing model (compare Wikipedia)
• Question to behavioural scientists - how can
we engage the stakeholders to use it?
– Professionals
– Patients
– Providers
• “The problem is in the implementation” …
incentives, bonuses, payoffs, …?