1. Representing Dispositions
Johannes Röhl/Ludger Jansen
Universität Rostock
DFG-Projekt Good Ontology Design
UNIVERSITÄT ROSTOCK | PHILOSOPHISCHE FAKULTÄT

2. Dispositions and their relations Simplifying assumptions
Overview
Motivation – what are dispositions and why are they useful in biomedical ontology?
Dispositions and their relations
Simplifying assumptions
Binary formal relations
Principles for surefire dispositions
Outlook
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3. Motivation: Dispositions are frequent in biology and medicine
disposition terms in SNOMED CT (including „tendency“, propensity): Tendency to bleed, tendency to nausea and vomiting, propensity to adverse reaction to food
drugs like aspirin have abilities to relieve pain, molecules have dispositions to undergo certain chemical reactions under certain circumstances etc.
Generally: We have a vital interest in what could happen, e.g. to prevent something bad from happening by taking precautions
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4. Examples: fragility, solubility
What are dispositions?
A Disposition is a property that is linked to a realization, to a behavior an individual with that disposition will show under certain circumstances or as response to a certain stimulus (trigger).
Examples: fragility, solubility
x has Disposition D implies the counterfactual conditional:
if x was under circumstances C, x would exhibit behavior R (the realization of the disposition).
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5. Dispositions, interactions and causality
Dispositions provide a link between types of particulars (the bearers of the dispositions) and types of processes and interactions these particulars are involved in:
„The dispositions of things are thus essentially linked to kinds of processes, and every manifestation of a disposition must exemplify some kind of process.“
(Ellis/Lierse: “Dispositional Essentialism”, in Australas. Journal of Philosophy 1994)
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6. Diseases as dispositions
Goldfain, Smith, Cowell 2010: „Dispositions and the Infectious disease Ontology“ (following OGMS)
disease as triple of distinct aspects <disorder, disposition, course of disease>
disease is a disposition towards pathological processes
disorder is the non-dispositional basis (structure of properties)
course of disease is a realization of the disease (as disposition), a process
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7. Diseases as dispositions
disease as triplet <disorder, dispositon, course of disease>
disease is a disposition towards pathological processes
Drugs/Treatments as „antidotes“ with dispositions that counteract the disease, so the pathological processes are not realized fully.
Distinction allows various disease courses and symptoms to be realizations of one and the same disorder.
Dormant or latent disease: patient carries infectious agents but shows no symptoms
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8. Dispositions in BFO (Basic Formal Ontology)
BFO Category
....
dependent continuant
└ quality
└ realizable entity
└ function
└ role
└ disposition
→ Necessary relations:
realization (process)
bearer (indepedent continuant the disposition inheres in)
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9. Possible Relations of a disposition
Additional conditions Ci
trigger T
(process)
Probability P
Disposition
Realization process
bearer x
(material entity)
x has disposition D for realization R with probability P under circumstances C and trigger (Stimulus) T.
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10. Dispositions and their relations
x has disposition D for realization R with probability P under circumstances C and trigger (Stimulus) T.
6 relata!
Independent continuant x
Disposition D
Realization R (process)
Probability P
Circumstances C
Trigger T
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11. Dispositions and their relations
Descriptions Logics can deal well with binary relations only
Simplify!
Independent continuant x
Disposition D
Realization R: process
Probability P only „surefire dispositions“
Circumstances C too general, ontologically not clear
Trigger T: process, initiation of change
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12. Dispositions and their relations
Still to many relata as Description logics admits only binary relations
Split up in several binary relations:
x has_disposition d
d has_realization r (only one type „single track disposition“)
d has_trigger t (only one type „single trigger disposition“)
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13. Primitive relations
Take following (token level) relations as established (OBO, Smith et al )
x instance_of X between a particular and its classes (both for processes and continuants)
p has_participant x between particular processes and particular continuants
q inheres_in x between individual instances of dependent and independent continuants (cf. Schulz/Jansen 2009, 23)
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14. Relations I - has_disposition
x has_disposition d := D d instance_of D  D is_a Disposition  d inheres_in x
if a disposition is essential for a type of continuant (all aspirins have the disposition pain relief) it will hold between types:
A has_disposition D := x: x instance_of A → y: y instance_of D  y inheres_in x
Subrelation of has_property (Schulz/Jansen 2009)
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15. Relations II - has_bearer
Inverse of x has_disposition d: d has_bearer x
subrelation of inheres_in
like any property every disposition instance needs a bearer, but they do not have to be of the same type. Different drugs are bearers of the same disposition pain-relieving.
If a disposition inheres only in one type, define type relation:
X has_bearer Y := x: x instance_of X → y: y instance_of Y  x inheres_in y
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16. Relations III - has_realization
connection of a disposition instance with the process instance it is a disposition for, its realization.
Generalization cannot exhibit the “all-some”-structure:
“For all instances x of D there exists a process instance y of R such that x has realization y” is clearly wrong! Otherwise all dispositions would always be realized, but some may never be, because the triggering circumstances are never met.
Use instance level d has_realization r as primitive ontological and causal connection.
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17. Relations III - has_realization
Suggestion for a corresponding type level relation has_realization:
A type of process R is the realization type of a disposition type D if and only if any instance of D is realized, then the realization is of type R:
D has_realization R :=
x (x instance_of D → y: x has_realization y → y instance_of R)
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18. Relations IV - has_trigger
We can split the fundamental nexus <disposition, trigger, realization> in two ways:
relation between the triggering process and the disposition, e.g. between the fragility of a glass and its dropping.
d has_triggerDt
relation holding between triggering process and the realization of the disposition (the dropping of the glass triggers its breaking).
r has_triggerR t
d has_triggerDt r (d has_realization r r has_triggerR t)
r has_triggerR t  d (d has_realization r d has_triggerD t)
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19. Relations IV has_trigger
Trigger instances exist only for those particular dispositions that become realized.
D has_triggerD T :=
x (x instance_of D → y (x has_triggerD y → y instance_of T))
R has_triggerRT
if only one type T of trigger for R, all-some-structure holds:
For all r instance_of R there is some t instance_of T and
R has_triggerR T.
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20. Principles for sure-fire dispositions I
„Realization principle“
if a disposition and its trigger are given, the realization will happen:
( D D is_a Disposition  T T is_a Process R R is_a Process D has_triggerD T D has_realization R dd instance_of D t t instance_of T) → r r instance_of R
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21. Principles for sure-fire dispositions II
“Bearer Principle“
The bearer of the disposition is a participant of the realization process:
(D D is_a Disposition  T T is_a Process R R is_a Process D has_triggerD T D has_realization R dd instance_of D 
t t instance_of T  b b bearer_of d) → r (r instance_of R r has_participant b)
The converse will not hold as a process is in general the realization of several dispositions of the interacting participants.
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22. Relations between bearer, disposition, trigger and realization
independent continuant
has_participant
trigger (process)
has trigger (R))
has_bearer
has_participant
has_trigger(D)
Realization
(process)
Disposition
has_realization
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23. „Multi-track“ and „Multi-trigger“
Something fragile does not always have to break into pieces, if struck, dropped or put under stress it may show cracks or splinter etc.
No unique relation disposition - realization
Option 1: fine-grain dispositions in such a way that multi-track dispositions are always resolved in many single-track ones.
X has D1 with R1, T1,
X has D2 with R2, T2
Probably not convenient for medicine, as one and the same disease may have different disease courses as realizations.
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24. „Multitrack“: one disposition - different realizations
Option 2: Allow diverse realizations
Disjunctive list of possible realizations, often not mutually disjoint, but inclusive:
Realisations of type of influenza: fever OR nausea,
fever AND nausea etc.
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25. How to deal with general realization conditions?
Outlook
How to deal with general realization conditions?
How to deal systematically with multi-trigger and multitrack?
How to combine dispositions for joint effects (like vector addition of forces)?
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