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FULL TITLE

Dynamic Coalitions

Keywords

 

SUMMARY

This work has been motivated by work within the GOLD project, which seeks to build an architecture to facilitate the creation and maintenance of Virtual Organisations within the Chemical Engineering sector, and DSTL.

Dynamic Coalitions and Virtual Organisations are often seen as two terms for identical concepts, even though the terms themselves can take on a wide range of meanings. Within the School of Computing Science at Newcastle, a group has been working to develop a common understanding of Dynamic Coalitions. Here we set out our common position, insofar as one has been achieved. This page is a summary of Dynamic Coalitions: A Position Paper, which was presented at the 2005 DIRC project workshop.

Dynamic Coalition situations

Dynamic Coalitions emerge when the individual interests of a number of parties are considered to be best served by co-operation with each other. Within a political context, the OED defines coalition as "An alliance for combined action of distinct parties, persons, or states, without permanent incorporation into one body." We can step from politics into many other contexts, by allowing these "parties, persons or states'' to also include companies, software or hardware agents, web-services and military units, among others. The word "dynamic" points to the nature of the alliance mentioned above.

A dynamic coalition may be formed spontaneously, members may join and leave without warning, and the nature of the relationships between participants may vary dramatically across the coalition as well as throughout its lifetime. Dynamic coalitions are distinct from a collection of interacting parties by having a common goal or intention. Each party may have several goals, and some of these may be in conflict with those of other parties in the coalition, but the common goal is sufficiently strong for them to choose to form a coalition together.

Dynamic coalitions occur in many settings, for example: In response to an emergency, where dealing with the immediate emergency becomes the over-riding interest of each party. This will be a dynamic grouping, because as the focus of the problem changes the necessary capabilities will be better supplied by different parties. For example, in the event of an earthquake, immediate evacuation of the area may be crucial and require the rapidly deployable capabilities of the army; later the health of the refugees may become the focus, requiring the intervention of the Red Cross. In response to commercial market forces, where each company believes that profitability will increase if they cooperate. In this context, they are often referred to as Virtual Organisations or Virtual Enterprises.

For example, in the Chemical Engineering sector, the patent-holder of a drug will have only a finite amount of time to manufacture and sell the drug before any other company may also exploit the same drug. If a company does not have all the necessary manufacturing skills ``in-house'', it may reduce its time-to-market by forming a suitable coalition to compensate for the missing techniques. It will then have more time to exploit its monopoly. In a programmed-agent context, where the agents have been designed to use input from other agents or sensors around them. These are called multi-agent systems. As the communications topology changes, agents will have to continually reconfigure their "dynamic coalition'' of communications with the other agents in order to maintain some desired functionality.In a military context, where achieving an objective may require the cooperation of a large number of military units. Here the dynamic nature of the cooperation could be due to new objectives becoming necessary as the conflict evolves.

Formal modelling

We are interested in the flow of information around these models of coalitions. For example, we are interested in identifying states of formal models in which information has reached the "wrong" actor, or where information has not reached the "right" actor. The purpose of the formal modelling will be to identify these states. We therefore intend to model a theory of knowledge distribution in a distributed environment in which dynamic coalitions form, change and disperse.

To do this we will develop a formal model, within which we can specify a number of overlapping dynamic coalitions. We will begin with as simple a model as possible and continue by building an increasingly refined set of formal models.

Our formal model will at least be able to describe the following properties:

1. Parties may know (or believe) different things.

2. Information will be "time-valued" --- items of information may become more or less valuable to parties over time.

3. Different parties may make different inferences from the same pieces of information. We have begun work on a simple formal model which will contain these elements.

We have said above that the purpose of our formal modelling will be to identify potential interesting or problematic information flow properties within coalitions. This will lead us to identify the behaviours of the individual parties that led to these properties.

After this, we may be able to make some deductions about the motives of the parties for these behaviours. For example, trust is an important aspect of dynamic coalitions. Differing trust relationships may lead to differing behaviours which may lead to differing information flow outcomes. It may be possible at a later stage of development to ascribe trust models or policies to the actors. These would essentially act as a set of constraints on the possible behaviours of the coalition.

We have also considered the question of access control policies to information within Virtual Organisations. At any one time, the "policy" of a VO will be made up of the different policies that each individual member of the VO maintains, as well as any agreed group policy. It is therefore important that we are able to manipulate and analyse access control polices in a formal way. To make this possible, we have begun to work on translating the access control markup language XACML (which has no formal semantics) to CSP, in order to reason about polices using the CSP semantics. Initial work is reported in Reasoning about XACML policies using CSP

Links

Gold project website

VDM Resources

VDM files to download

Papers

The Dynamic Coalitions Coalition. Dynamic Coalitions: A Position Paper. Presented at the DIRC project workshop, 2005.

Jeremy Bryans. Reasoning about XACML policies using CSP. Technical Report TR-924, School of Computing Science, University of Newcastle, July 2005.

Authors

Jeremy Bryans, John Fitzgerald, Cliff Jones and Igor Mozolevsky (University of Newcastle)

 

 
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