Visualisation of CaseBase Reasoning for Explanation

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Visualisation of Case-Base Reasoning for
Explanation
Stewart Massie Susan Craw
Nirmalie Wiratunga
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Outline

• Motivation
• Problem Domain Tablet Formulation
• What Needs to be Explained
• Embedded Knowledge used in the CBR Process
• The Solution
• FormuCaseViz
• Parallel Co-ordinate Approach
• Ordering the Attributes
• Software Demo
• User Evaluation
• Conclusions

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Motivation

• Low Acceptance of new Technology by Users

Scared of Innovation
It doesnt work
Belief that it doesnt work

• How does this affect CBR Systems
• Easily understood methodology that doesnt
  require explanation? - FormuCase

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Tablet Formulation Problem

• Tablet consists of more than a drug
• Recipe of Inert compounds (excipients)
• Filler, binder, lubricant, disintegrant,
  surfactant
• Formulation is choice quantity of each
• It is a component-based design problem
• Small number of components (five)
• Selected from a list of possible excipients

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FormuCase -Representation

• Problem
• 4 Physical Properties (e.g. solubility, yield
  pressure)
• 20 chemical stabilities with possible excipients
• The Dose
• 25 Numeric Attributes in total
• Feature-Value representation

case
problem
solution
disintegrant
filler
binder
lubricant
surfactant
filler
surfactant
drug
disintegrant
binder
lubricant
dose
physical
excipient
excipient
excipient
excipient
excipient
chemical properties
amount
amount
amount
amount
amount
properties
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2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
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25
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31
32
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feature
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FormuCase - Solution
Reaction to FormuCase was Neutral
No Explanation
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What Needs Explaining

• Embedded Knowledge
• Case Representation
• Case base
• Retrieval Process
• The Solution
• Coverage in Target Problem Neighbourhood
• Differences between Retrieved Cases Target
• Differences Within Retrieved Cases

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Why is Explanation Needed

• Aids user understand decision making process
• Allows user to judge the appropriateness of the
  embedded knowledge
• Make uncertainty in the solution visible
• Allows deficiencies to be identified
• Increases user confidence

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FormuCaseViz - Parallel Co-Ordinate Approach

• Displays multi dimensional vector in 2
  dimensions
• Attribute represented by labelled vertical axis
• Case represented by line across each axis
• Clusters of cases can be discerned

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FormuCaseViz-Ordering Attributes

• Similarity between Axes calculated across the
  cases

A1
A2
c1
c2
0
0
(0.6-0.2)2 (0.3-0.7)2 ...
c1
0.2
c2
0.3
c3
0.5
c1
0.6
c2
c3
0.7
0.7
1
1

• Linear arrangement - similar axis next to each
  other

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User Evaluation

• Evaluate how well FormuCase and FormuCaseViz
  explain their solutions
• Two domain experts from PROFITS
• Key Points They Highlighted
• Reluctance to accept a single similarity value
• Visual approach makes interpretation of results
  easier
• FormuCaseViz shows similarities differences
  very clearly
• FormuCaseViz is better at explaining its
  reasoning
• Cannot read numerical values directly from
  FormuCaseViz

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Conclusions

• User Confidence Requires
• Correct solutions
• But also Requires
• Explanation of Decision Making Process
• Ability to Identify Potential Deficiencies
• Eye is good at identifying patterns and
  exceptions in data
• Our Visualisation Approach
• Overlaps in problem solution features
  demonstrates support
• Differences highlight variability

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QUESTIONS
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FormuCase - Tablet Formulation Problem
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Related Work

• Decision Tree Retrieval
• Cunningham (ICCBR03)
• K-NN Retrieval
• Explanation beyond merely similarity (Hotho et
  al. 2003)
• Supporters Opposers
• McSherry (UKCBR Workshop 03)
• Visualisation Approaches
• Spring model (McArdle Wilson03)
• Parallel Co-ordinate (Falkman ECCBR02)

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Motivation

• FormuCase
• Problem domain
• Initial textual solution
• Where did we go wrong no explanation

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FormuCaseViz-Ordering Attributes

• Order of attributes can improve visualisation
• Similarity between Axes calculated
• Similarity calculated across the cases
• Linear arrangement with similar axis next to each
  other
• Analogous to TSP Problem NP Complete
• Simple approach
• Ordering Similar Axes beside Each other
• Reduces line crossing
• Helps identify trends

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FormuCaseViz - Problem
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FormuCaseViz - Soloution