Formalising Dynamic
Coalitions
Budi Arief, Jeremy Bryans, John Fitzgerald, Carl Gamble,
Michael Harrison, Nigel Jefferson, Cliff Jones,
Igor Mosolevsky, Peter Ryan
15 March 2005
Jeremy Bryans
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Introduction
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An example Dynamic Coalition
Our aim
Formalising
Conclusions
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A Healthcare Dynamic Coalition
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Actors: patients with wearable thermometers +
blood sugar monitors, hospitals with various
machines, doctors, paramedics,
Structure: Collection of experts with different roles
(not necessarily a fixed hierarchy.)
Information: patient history, medical decisions,…
Communications:
 permanent links (e.g. between machines in
intensive care)
 transient links (e.g. wearable monitors)
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A Dynamic Coalition is…
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•
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A set of actors, possibly structured
Ways of communication:
 broadcast, mailing lists, one-to-one,…
Some common knowledge:
 e.g. definitions of common terms,
joining/leaving rules, …
Possible actions:
 Joining, leaving, creating a DC, (destroying a
DC?)
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Our intention
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“...to model a theory of knowledge distribution, in
which dynamic coalitions form, change and
disperse.” [position paper]
•
This means we need to have a (formal) model of:
 what a VO is;
 what knowledge is;
 how it is communicated.
(In fact, an increasingly refined family of formal
models.)
 And (at least) an animator for these models.
•
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Analysing information flows.
We wish to be able to model (at least) the following
properties:
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Parties may know different things.
Information has value. (as an asset)
 The value of information may change over time.
Different parties may make different inferences
from the same pieces of information.
 Or the same inference from different pieces of
information.
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•
•
•
•
An example Dynamic Coalition
Our aim
Formalising
Conclusions
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the state model
C1
A1
A3
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A2
C2
A3
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the agent model
A “Cid” maps to all knowledge associated with that coalition.
“null” maps to everything that the agent knows.
E.g.
null
k1,k2,k3
k4,k5,k6
C1
k1 k5
k3
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C2
k3
k2 k4
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A modelling example
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Question: How to model provenance of
information?
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solution 1 (BSCW)
Every bit of information is (globally) associated
with a single originator.
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solution 2 (who told me what)
Every agent associates each KId they
know with a single originator.
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solution 3
Every agent associates each KId they
know with a sequence of agents. (full audit trail)
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Further complications
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People could lie about where information arises,
 or refuse to tell
“Some senior government source”
You may have two sources for the same
information
 but you may not trust one of them
…
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Conclusions
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Can quickly describe what we mean.
Can see how new features interact with earlier
ones.
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Possible view of an animator
Possible scenarios in
(from a model-checker?)
model
e
d
a
c
Scenario 1
Join (a,b)
Unjoin(b,e)
b
Share_info (x,b,d)
Possible questions
Who knows information “x” ?
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Does anyone have sufficient
information to calculate y ?
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Tracing information
actor
communication
knowledge
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Information flow model
high user
system
BOUNDARY
low user (adversary)
System = common computer…?
What information can flow across the boundary?
Given Low’s knowledge of SYSTEM,
He may be able to infer information about high activity.
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A Dynamic Coalition is…
•
•
•
•
A set of actors
Ways of communication:
 broadcast, mailing lists, one-to-one,…
Some common knowledge:
 e.g. definitions, joining/leaving rules, …
possible actions:
 Joining, leaving, creating a DC, (destroying a
DC?)
15 March 2005
Jeremy Bryans
DIRCshop
33