Title: Expert Knowledge Elicitation
1Expert Knowledge Elicitation
2Assume
- Knowledge intensive processes are driven and
constrained by the mental models of experts - Product development is guided by expert knowledge
- Critical process relationships that are dynamic
- Biased by individual perspectives and goals
- Conditioned by experience
- Aggregate many system components and
relationships - Are often nonlinear
3Mental models
- A mental model represents one possibility,
capturing what is common to all the different
ways in which the possibility may occur. Mental
models represent explicitly what is true, but not
what is false. These characteristics lead naive
reasoners into systematic errors. - The greater the number of models that a task
elicits, and the greater the complexity of
individual models, the poorer performance is.
Reasoners focus on a subset of the possible
models of multiple-model problems - often just a
single model - and are led to erroneous
conclusions and irrational decisions. - Procedures for reasoning with mental models rely
on counterexamples to refute invalid inferences
they establish validity by ensuring that a
conclusion holds over all the models of the
premises. These procedures can be implemented in
a formal system most artificial intelligence
programs) do not use them.
http//www.tcd.ie/Psychology/Ruth_Byrne/mental_mod
els/theory.html
4Mental models Meadows
- Each person carries in his head a mental model,
an abstraction of all his perceptions and
experiences in the world, which he uses to guide
his decisions mental models are intuitive
generalizations from observations of real-world
events. (Meadows et al. 1974 4-5)
5Mental models Senge
- Mental models are deeply ingrained assumptions,
generalizations, or even pictures or images that
influence how we understand the world and how we
take action. Very often, we are not consciously
aware of our mental models or the effects they
have on our behavior. (Senge 1990 8)
6Mental models Sterman
- In system dynamics, the term mental model
stresses the implicit causal maps of a system we
hold, our beliefs about the network of causes and
effects that describe how a system operates, the
boundary of the model (the exogenous variables)
and the time horizon we consider relevant our
framing or articulation of the problem. (Sterman
1994 294)
7Cognitive psychology and dynamic systems design
- Cognitive psychology tends to examine theories of
knowledge represented in the mind as long term
memory - Mental models theory argues that there are
specialized cognitive structures in long-term
memory used for different tasks and situations - These are transforming and are often implicitly
held - Some argue that novices tend to use models and
experts rely on abstract rules - Researchers also propose that there are a large
number of specialized cognitive structures that
act in long-term and short-term memory storage
and recall - Scripts and schema
- Most research using mental models is
interdisciplinary as in human-computer-interactio
n (HCI)
8Role in deductive reasoning Laird-Johnson
- A mental model can be defined as a
representation of a body of knowledge either
long-term or short-term that meets the following
conditions 1. Its structure corresponds to the
structure of the situation that it represents. 2.
It can consist of elements corresponding only to
perceptible capable of being perceived by the
senses entities, in which case it may be
realized as a image, perceptual or imaginary. 3.
Unlike other proposed forms of representation, it
does not contain variables In place of a
variable a model employs tokens symbols that
are fixed rather than capable of assuming
alternate values or states (Laird-Johnson 1989
488)
9In HCI
- knowledge about the system, external influences,
and control strategies (Veldhuzen and Stassen
1977) - Special types of schema (Jagacinski and Miller
1978) - mental representations of a system (Young 1983)
- organized structures consisting of objects and
their relationships (Staggers and Norcio 1993) - abstract concepts that represent a persons
knowledge of a decision problem (Coury et al.
1992) - representations that are active while solving a
particular problem and that provide the workspace
for inference and mental operations (Halford
1993) - a persons understanding of the environment It
can represent different states of the problem and
the causal relationships among states (Shih and
Alessi 1993) - a mediating intervention between perception and
action (Wild 1996)
10MMODS mental models of dynamic systems
- A definition must
- point out unique attributes or qualities of
whatever is - defined
- not be circular
- stated positively
- use clear terms
- (following Francfort-Nachmias and Nachmias
1992)
- a mental model of a dynamic system is a
relatively enduring and accessible, but limited,
internal conceptual representation of an external
system whose structure maintains the perceived
structure of that system. (Doyle and Ford 1998)
11Research potentials
- Mental models provide a unified account of
deductive, probabilistic, and modal reasoning. - Current challenges to model theorists are to
explain - causal reasoning
- deontic reasoning about what is permissible and
impermissible - defeasible reasoning in which the facts demand a
change in one's beliefs - strategic thinking that occurs in making
decisions and in reasoning about another
individual's inferences.
http//www.tcd.ie/Psychology/Ruth_Byrne/mental_mod
els/theory.html
12To portray mental models
- Key parts
- An image (needed if the mental model is of a
physical thing) - A script (needed if the mental model has a
process) - A set of related mental models
- A controlled vocabulary
- A set of assumptions
http//www.boxesandarrows.com/archives/whats_your_
idea_of_a_mental_model.php
13Tacit knowledge may drive expert decisions
- Tacit knowledge is difficult to describe, examine
and use - Improvement of complex processes has
- False starts
- Failures
- Institutional and interpersonal conflict
- Policy resistance
- Modelers have difficulty in eliciting expert
knowledge and representing expert knowledge as
useful models
14SIGGI as neural agent uses the knowledge model
- Interdisciplinary teams are required to build the
AI system - Knowledge elicitation of system builders and
operators required to structure and parameterize
the model - To build a useful model, modelers must elicit
from experts information about system structure
and governing policies
15Tacit knowledge
- Tacit knowledge is
- Subjective
- Personal
- Context-specific
- Modeling requires
- Elicitation
- Articulation
- Description of expert knowledge
16High-tech product development
- Drives expert knowledge elicitation
- This requires multiple knowledge-driven processes
- Design to produce the final product
- Quality assurance that transforms unchecked
designs into approved designs or designs
requiring changes - Critical process relationships are dynamic,
nonlinear, biased by individual perspectives and
goals, conditioned by experience, and aggregate
system components and relationships
17Standard KE practice
- Knowledge elicitation techniques are generally
used for - Problem definition
- Model conceptualization
- Model boundary definition
- Recognized factors
- Purpose of the modeling effort
- Phase of the model-building process and type of
task performed - Number of people involved
- Time available
- Cost of the elicitation methods
18Formal modeling requirements
- Goal description of tacit expert process
knowledge with detail an dprecision to improve,
complex, tacit models requires description of
relations at an operational level - Formal modeling requires specification of data,
functional forms, and numerical estimates of
parameters and behavioral relationships
19Situational model
Endsley 2000 Figure 1.
20Series of situation models
Endsley, English and Sundararajan 1997
21SAGAT situational awareness global assessment
technique
Endsley, English and Sundararajan 1997
22Parameter elicitation
- SIGGI is a unique contribution in this regard
- Little in the literature on estimating functions
and parametric relationships ( archaeological
types) - Reference curves constructed
- Identify reference points
- Much of the skill is tacit, passed on from
teachers to students in apprenticeships
23Metaphor-analogy-model
- Objective of most methods is development of
conceptual designs and models ( concept
development) - Nonaka and Takeuchi (1995) look at
organizational knowledge in 3 steps - Describe system knowledge with metaphors
- Integrate metaphors with analogies
- Model the resulting product concepts
- (research in Japanese self-organizing teams)
- product rough, non-specific descriptions or
drawings
http//portal.acm.org/citation.cfm?id69173 http/
/jasss.soc.surrey.ac.uk/4/1/reviews/renault.html
24Metaphor
- Common def. a figure of speech that suggests a
similarity between two nonidentical things. - Brown (2003) def. the phrase conceptual metaphor
means any nonliteral use of language that results
in a partial mapping of one term, image, object,
concept or process onto another to reveal
unsuspected similarities the phrase encompasses
similarity, metaphor, analogy, abstraction,
model, illustration, figure, hypothesis, theory
and mathematics observational data can be
related to models only through metaphors for
interpreting the data. - E.g., molecular models are metaphors because they
represent a mapping from the domain of pictorial
or three-dimensional model representation onto
the domain of data from X ray diffraction and
other experimental observations.
25Analogy
- all knowledge is rooted in metaphorical or
analogical modes of perception and thought - Metaphors and analogies move novices and
experts' mental models into to the unknown - Experts frequently use analogies to build bridges
from the known to the unknown. - Constraints of a good analogy
- Similarity The source of the analogy and the
target must share some common properties. - 2. Structure Each element of the source domain
should correspond to one element of the target
domain, and there should be an overall
correspondence in structure. - 3. Purpose The creation of analogies is guided
by the problem-solver's goals.
http//128.143.168.25/book/chap2/chapter2sec4.html
26Causal loop diagrams
- Burchill and Fine (1997) use causal loops to map
feedbacks in concept development for new products - Careful coding of participant comments
- Produces causal loop diagrams that capture
participant beliefs about processes governing
concepts - Does not yield quantitative information
27Formal model
- Ford and Sterman (1997) identify sources for
system dynamics modeling - Forrester (1994)
- mental expansive and rich in information
- written codified and more easily accessible but
lack richness, modelers cannot query for testing,
and it is by nature biased by the authors
viewpoint - numerical narrowest in scope and lacking in
supporting contextual information about the
generating structure - goal of generating a formal model pushes experts
- to describe relationships at the simulation level
- clarify and specify their knowledge
28Phased elicitation
- Ford and Sterman (1997) identify 3 sequential
phases - Positioning phase
- Description phase
- Discussion phase
29Positioning phase
- Establish context and goals for the description
process - Facilitator sets goals and provides structure
- Focus on one relationship at a time (graphic
frames) - Illustrate the method (relationship description
worksheets)
30Description phase
- sequential development of 4 different
descriptions of the relationship (no interactions
between experts) - visual description (activate, bound and clarify
mental images) - verbal description ( transform mental image into
explicit form and codify knowledge) - textual description (codified description of the
experts knowledge) - graphic description
- points plotted on an empty graphic frame
- experts identify relationships as graphs with no
direction
31Discussion phase
- seeks to test, understand and improve the
descriptions of different experts (Vennix and
Gubbels 1994 estimate-feedback-talk protocol) - examine individual descriptions (each expert
shares verbal and graphic descriptions) - compare descriptions (there will be differences
complexity in knowledge bases) - mental models will be identified and assumptions
examined - no attempt is made to resolve differences or
reach consensus
32Advantages of sequential phase model
- information losses during elicitation are reduced
compared to single-step processes through use of
several small, separate and explicit format
transitions - the generation of multiple descriptions in
different formats by a single expert allows
testing and improvement through triangulation - the generation of multiple individually-generated
descriptions in a group context allows testing
and improvement of descriptions through
comparison to the views of other experts while
reducing the potential for group-think and
premature convergence
33Sequential phase model structure
Ford and Sterman 1997 Figure 1
34Positives
- method helps generate useful products reflecting
community assessment - models are improved (cf. Morecroft 1994)
- verbal and textual descriptions provide data for
triangulation - behavior pattern validation is improved through
better model calibration by drawin upon expert
knowledge - model analysis is improved by using experts
assessments to select the ranges of variation as
parameters and relationships - structural behavior validation is enhanced by
setting limits on extreme conditions of important
model parameters - formal model credibility is improved in the view
of the participants by adding multiple experts to
the knowledge base
35Actions
- Knowledge held in mental models is usually not
described in other forms because it is complex
and tacit - KE model uses multiple formats to elicit and
capture this expert knowledge - use of descriptive formats adds richness to
improve information quality through triangulation - individual experts seek consistency among their
descriptions of a particular relationship - experts compare their different descriptions
- use of graphical representations through
successions of small steps reduces cognitive
processing required of system experts - explaining and providing complete documentation
of the steps to be performed improves
descriptions and experiences of experts - effort is expended on knowledge that experts
consider important and proprietary - discussion provides immediate benefits to experts
by allowing them to share and compare mental
models in a form that facilitates learning by
investigating underlying assumptions - the process of describing and comparing
individual descriptions in groups of peers
increases error checking
36Prognosis
- Goal 1 SIGGI training Situation models (Endsley
2000) work well to create computer models that
perform as well as human models - Goal 2 model to understand archaeologists
thinking create a model that designers can use
to better understand human mental representations - Proviso neural networks, because they utilize a
learning approach to generate knowledge, can be a
black box and provide little insight into how
decisions are actually made
37Expert systems as cognitive emulations
- In an expert system a rule contains an antecedent
and a consequent (Barcelo 2001) - The antecedent enumerates situations in which a
rule is applicable - When conditions are true, knowledge in the rule
consequent has been activated - The expert system in reality contains hundreds of
rules and the associations between different
units is complex - Consequences of determined rules will condition
activation of others
- If A and B, then C
- If x is X, then D
- If C and D, then H
- If B, then D
38Modalities of reasoning
- Given empirical data (observations) about a
specific archaeological case - Given a set of rules (If .. Then or hypotheses
and interpretations considered valid ) - The explanation is constructed in terms of
knowledge stored in the rule base
39Activating knowledge units
- Two criteria
- A unit of knowledge
- An association between this unit of knowledge and
the unit of knowledge to be proved - By defining associations, the activation of a
concept will expand automatically, in turn
triggering activation of new concepts - Following Anderson (1983), the different expert
system hypotheses will activate according to the
relations maintained with the possible sources of
activation (hypotheses previously activated and
with which it is associated
40The expert system works
- Because the inference engine causes a cascade
movement between different knowledge units - If too narrow little utility
- If too broad too many possible interpretations
- Activation of knowledge units is not in computer
code and is part of the concept of abduction
(Josephson et al. 1987)
41Abductive inferences
- Abductive inference syllogism
- D is a collection of data (observations expressed
in terms of verbal descriptions, numerical
measures, digitized images) - H explains D (If H were true, then would imply D)
- No of the Hypotheses explains D better than H
- Then, H is correct
- If (x,y,z) are proper empirical features of
Object F1 - And (v,W) are proper definition terms of Concept
F - Anth there is some association (is-a) between F
and F1 - Then F1 activates F
- Object (F1) is an instance of Concept F
Barcelo (2001)
42Practicality
- Thagard (1988) admonishes that we establish a
heuristic connection between two knowledge units
based on practicality A explains B because A
fulfills stated requirements - The requirements are formal or quasi-formal
- These are derived from the stated goals
- We can have 1. A formal definition or 2. have an
association a heruistic association
43Expert knowledge used
- Using necessary information is controlled by
prior knowledge about the problem
(meta-knowledge) - This knowledge allows the designer to stipulate
conditions that successive states of the problem
should fulfill to become an approximation of the
solution
44Gardin et al. 1987 on Expert Systems concerns
- 2 groups of 6 reservations
- Group 1
- Fragmentary nature of representations
- Arbitrary nature of the factual base
- Awkwardness or ill-fit of the rules drawn
- Group 2
- Construction of definitions from vague terms
- Use of analogies that not constructed upon
underlying calculations based on measurement and
probability coefficients - Overall undertaking perhaps more akin to
improvisation than science - Many archaeologists think expert systems
oversimplify, force knowledge, distort knowledge,
and do not fully exploit expert knowledge (cf.
Francfort 1993 308)
45Following Barcelo
- Archaeological explanation can be represented as
series of successive actions leading to empirical
description - These actions are in fact operators that function
to link the initial state (description) to the
final state (explanation) - The problem space in effect constitutes a framed
theory - There should be a finite set of independent
operations, each with its own heuristic validity
criteria (propositional or topological) - Fuzzy thinking and non-monotonic expert systems
avoid pitfalls of natural language discourse - The truth value of concepts becomes their
applicability in schemata of action
46Expert System SIGGI-AACS
- SIGGI is
- a Neural Agent
- who Learns Rules
- and Thinks Creatively
47SIGGIs Thoughts
- To train a neural agent in an AI system we must
make implicit referential systems explicit - We extract expert knowledge and create
hierarchical structures or decision trees - Siggi learns to think like an archaeologist
- But Siggi has reference to much more
authenticated data
48SIGGI Prototype
- Domain Expert Lohse (1985), Columbia Plateau
cultural area - Rufus Wood Lake projectile point chronology used.
- Large collection with established provenience and
radiocarbon dates.
- Lohse classification chosen because it was
explicitly based on established types, - had clean provenience information,
- a suite of radiocarbon dates,
- a clear analytical framework,
- and was statistically driven.
49Expert Training Lohse 1985
- SIGGI has currently been trained to employ the
classification system developed by Lohse (1985)
for the Columbia Plateau - Explicit
- Statistically based
- Authenticated data
- Community acceptance
501st Order Rules Lanceolates
- Variable forms are reduced to abstract geometric
ideals - SIGGI is taught that this is important and that
this leads to further distinctions
511st Order Rules Triangular
52Classifying Points in Multidimensional Space
- Handles real-world variability
- Creates measurable relationships
- Defines polythetic sets that offer discrimination
between types - Constructs discriminant functions that
distinguish between sets and individual specimens - Allows continued classification and objective
assessments of class relations as the dataset
expands
53Series centroid plots
- 6 morphological type series
- Clear statistical separation
- Simple lanceolate and side-notched series show
greatest separation
54Discriminant functions
- A mathematical function is a Cartesian product of
a set by itself where each pair of the product is
assigned a real number - Relations are sets of ordered pairs where
functions are sets of ordered triples - Measured points can be placed in matrices and
distances plotted (correlation matrices)
55Rotated standardized discriminant function
coefficients, lanceolate run (Lohse 1985)
- F1 haft length
- F2 neck width, blade width, shoulder angle,
shoulder length - F1 and F2 adequately explain 91 of the variation
in lanceolate types
Table 11-6, Lohse 1985
Conclusion for lanceolates, haft length and
development of well defined shoulders, coupled
with blade width and neck width are the major
variables used to distinguish recognized
lanceolate from shouldered lanceolate types.
56Rotated standardized discriminant function
coefficients, triangular run (Lohse 1985)
Table 11-7, Lohse 1985
Conclusion for triangular points, variance in
form is more subtle than in Lanceolate types,
and the primary discriminating variables are
shoulder Angle, basal margin angle and stem size
or overall proportion, reflected in Basal width
and the ratio between neck and basal width.
57Canonical Discriminant Runs, Lohse (1985)
58 Cases correctly classified, Lohse (1985)
59Rufus Wood Lake Projectile Point Chronology
Modal types - descriptive - historical
60Measurement Grids
Triangular Forms
Lanceolate Forms
61SIGGI doesnt use discriminant analysis
- SIGGI is short for use of sigmoid functions as
part of curve fitting related to form recognition - Sigmoid functions are often used in neural
networks to introduce nonlinearity in the model
and to make sure that certain signals remain
within a specified range. - A popular neural net element computes a linear
combination of its input signals, and applies a
bounded sigmoid function to the result this
model can be seen as a "smoothed" variant of the
classical threshold neuron.
http//www.answers.com/topic/sigmoid-function
62Curve fitting sigmoid functions
http//mathworld.wolfram.com/SigmoidFunction.html
63Actual outlines are reduced to geometric forms
- Objects defined in a descriptive system can be
conceived as points in space, whose dimensions
are descriptors of the objects - - 2D space (2 measured axes elements in the
vectors) distributions are regular, linear,
clustered or random - - 3D space (Euclidean 3D space 5D etc.
coordinates constitute vectors) clusters now
occur in multiple dimensions - N2 clusters in the 5 empirical dimensions
constitute 2 new abstract dimensions composed of
multiple descriptors
64Importance of Latent Dimensions
- Data elements are transformed into latent
dimensions in order to manipulate solutions at
the abstract or symbolic level - Latent dimensions can be found easily on the
computer - The latent dimensions are archaeological
structures ( polythetic sets) - Identification of latent dimensions allows
removal of unnecessary information using Bayesian
inference models
http//reach.ucf.edu/aln/pyle/theory.html
65Intersecting Variables
66TYPES
- RULES FOR INCLUSION OF DATA
- 1- A defined type must have a clearly proscribed
range of variation defined quantitatively or
qualitatively - 2- The named type must have been recovered in
definable archaeological contexts, and is
isolatable in specific stratigraphic sequences
67SITES
- RULES FOR INCLUSION OF DATA
- 1- Sites must have been excavated in cultural
stratigraphic levels and not in natural or
arbitrary levels. - 2- Provenience information must be available for
all recovered artifacts that specifies cultural
units as to stratum, feature and association. - 3- A detailed descriptive report covering
excavation methodology and analysis must be
published for the site or be in the process of
publication, and excavation notes and photographs
must be on file at a recognized repository.
68ASSEMBLAGES
- RULES FOR INCLUSION OF DATA
- 1- An artifact distribution to qualify as a site
activity assemblage must be defined in a discrete
vertical and horizontal distribution associated
with a recognizable cultural feature. - 2- The cultural and natural stratigraphy must
indicate that the assemblage represents a
discrete prehistoric activity. The assemblage is
not an analytical construct but a found context. - 3- The assemblage indicates a discrete series of
tasks or task-related activities. The assemblage
is not an amalgam of activities over an extended
period of time reflecting different seasons of
site use nor different uses in different years.
69TYPES AND ASSEMBLAGES
- Assemblage Windust
- a composite
- Types Windust, Cascade and Cold Springs S-n
- Windust and Cascade
- are distinctive to region (cultures)
- Large Side-n non-
- distinctive as regional
- indicator ( associated
- temporal marker)
Ames et al. 1998 reproduced from Leonhardy and
Rice 1970
70Inspection of Interstices
71Plateau Arche-Types
Rabbit Island
Cascade
Windust
Lind Coulee
72Plateau Archetype Schema
73Common Structures
74Middle Archaic C-n Forms
How to identify common and unique types?
Columbia Plateau these are Columbia C-n, large
and small Plains these are Pelican
Lake specimens Basin these are Elko
C-n specimens
http//www.abheritage.ca/alberta/archaeology/i_pel
ican.html
75Late Archaic S-n Forms
How to identify common and unique types?
Columbia Plateau these are Plateau S-n Plains
these are Avonlea specimens Basin these are
Desert S-n specimens
http//lithiccastinglab.com/gallery-pages/avonleag
rouplarge.htm
76SIGGI as a user-defined smart interface
77Loading images
78Defining outlines eroding
79Simple outlines
80Probabilities of membership morphological
categories
81Probabilities of membership Historical types
82To Do
- Obtain information from domain experts
- Columbia Plateau
- Northwestern Plains
- Great Basin
- Classify methods by interactions with domain
experts - Classify by types of information elicited from
domain experts
83Expert Interactions 1
- Interviews (concept mapping, cognitive structure
analysis, data flow models, task action mapping) - Case Studies (context-driven)
- Protocols (actions and mental processes)
- Critiquing
84Expert Interactions 2
- Role Playing
- Simulations
- Prototyping (expert evals, iterative system
evals, rapid prototyping, storyboarding) - Teach-back
- Basic observation
85Need for authenticity
- Only data that can be verified will be entered
into the database - used to train SIGGI
- used to test SIGGI
- Explicit rules for inclusion can be constructed
- sites to include
- assemblages to include
86Conclusions
- SIGGI was developed as
- an explicit classification system based on
accepted typologies - a smart user interface to
- manipulate large relational databases
- explore the nature of archaeological
classification - SIGGI as a prototype is smart enough to
- classify specimens into general accepted types
- begin explicit comparisons between cultural areas
- begin knowledge elicitation experiments with
archaeological experts
87Interface design
- Simplicity since mental models simplify reality,
interface design should simplify actual computer
functions. - Familiarity an interface should allow users to
build on prior knowledge, especially knowledge
gained from experience interacting in the world. - Availability an interface should provide visual
cues, reminders, lists of choices, and other
aids, either automatically or on request (users
emphasize recognition vs. recall). - Flexibility an interface should support
alternate interaction techniques, allowing users
to choose the method of interaction that is most
appropriate to their situation (users should be
able to use any object in any sequence at any
time). - Feedback a system should provide complete and
continuous feedback about the results of actions.
(feedback a user gets that supports their current
mental model strengthens it). - Safety a user's actions should cause the results
the user expects. - Affordancesan affordance refers to the
properties of an object (use real-world
representations of objects)
http//www.lauradove.info/reports/mental20models.
htm
88References
- Barcelo, Juan A., 2001, Expert systems as
cognitive emulation An archaeological viewpoint.
http//seneca.uab.es/prehistoria/Barcelo/ExpertEmu
lation.html - Brown, Theodore L. Brown, 2003, Making Truth
Metaphor in Science. Urbana University of
Illinois Press. - Ford, David N. and John D. Sterman, 1998, Expert
Knowledge Elicitation to Improve Mental and
Formal Models, System Dynamics Review 14(4)
309-340. - Nehaniv, Chrystopher L. (ed.), 1999, Computation
for Metaphors, Analogy, and Agents. Lecture Notes
in Artificial Intelligence 1562. Berlin
Springer-Verlag. - Nonaka, Ikujiro and Hirotaki Takeuchi, 1995, The
Knowledge-Creating Company, How Japanese
Companies Create the Dynamics of Innovation. New
York Oxford University Press. - Weidmann, Karl-Heinz, Metaphors, Conceptual
Models and Evolutionary Epistemology. -