An Agent-Based Virtual Organisation Scenario

This section describes a scenario in the CONOISE-G environment with the aim of contextualis- ing the use of trust in such an environment. A screenshot of the CONOISE-G system is shown in Figure 4.3, which shows the two main screens that allow a user to examine the state of the system.

VO FORMATION SCREEN Displays user requirements, registered SPs in the system, bids made by SPs and the VO

formed to meet the requirments.

VO FUNCTIONING SCREEN Simulates service provision from the VO, showing the QoS of the component services.

FIGURE4.3: A Screenshot of the CONOISE-G system.

The overall scenario is as follows:

“A user wants to purchase and receive a monthly movie subscription package on his PDA/phone, and a monthly news service. He also wants a monthly package for his PDA/phone that includes a certain number of free text messages and a minimum number of free minutes per month”.

The agents that are found throughout the scenario are described below, and the main interactions between them can be seen in Figure 4.4:

1. Yellow Pages Agent (YP) – This agent provides a lookup service, giving any agents the names/addresses/service descriptions of other agents upon request.

2. User Agent (UA) – This agent provides the initial bootstrap request for the Virtual Or- ganisation Manager agent.

3. Virtual Organisation Manager Agent (VOM) – This agent initiates the request for a service on behalf of a user-initiated request. It represents a front-end that the user can query and ask for a specific required service. It then forms a VO with other agents to provide that service, and manages the resulting VO.

4. Service Provider Agent (SP) – This agent provides one or more services that are sought by the user. The agent may provide the service in a number of different ways when a request for a service comes to it.

(a) It may provide the service itself.

(b) It may provide the service by using a VO it currently belongs to. (c) It may delegate the service provision to other agents.

Yellow Pages Agent Service Provider Agent User Agent VO Manager Agent 2. Request for a set of services 1. Register services 3. Ask for a list of

service providers for a particular set of services

4. List of service providers

5. Call for bids to service providers that can provide the required services

6.Each service provide responds with their own bid 7. VOM decides

best VO to form given bids

FIGURE4.4: The main agents in the scenario, and the interactions between them.

This scenario can be broken down into four main stages — system initiation, user querying, VO formation and VO restructuring — each of which involves different agents and interactions between these agents. The end result of this scenario is a system state in which there is a virtual organisation that meets the requirements of the user.

The rest of this section describes in detail the stages in seven discrete steps needed to achieve the requirements that the user requested, with emphasis on the need for trust in the environment.

Stage 1: System Initiation — The system is initiated.

Prior to any input or request from a user, the system must be initiated. In this phase, all the necessary agents are created and undergo a registration process with the YP agent.

Stage 2: User Query — Query is entered into the system.

Once the initial booting and registering process is complete, the system is ready. We assume that it has been operating for some time so that there is some interaction history in the system. After a while, the system receives a request by a user who wants to purchase and receive a monthly movie subscription package on his PDA, and a monthly news service. He also wants a monthly package for his PDA that includes a certain number of free text messages and a minimum number of free minutes per month. The system receives this query from a human user via the UA. It is important that the user trusts the UA and believes that the UA will successfully begin the process, which will result in the user receiving the services he requires.

Stage 3: User Query Forwarding — User agent forwards the query to a VOM agent.

Once the UA receives the query, it translates it into a common language that all agents in the system understand. It then evaluates the possible VOM agents to which it can delegate the responsibility of forming an appropriate VO to meet the user’s requirements. The UA uses its past interaction history (if it has any) in order to identify possible VOM agents and determine their trustworthiness. It then selects the most trusted VOM and forwards the user specification to the VOM agent.

Stage 4: VO Formation (a) — VOM identifies which agents can provide appropriate ser- vices.

In this stage the VOM uses the YP to identify which SP agents can provide the services required by the user. The VOM must trust that the YP agent is not colluding with a subset of the SP agents in order to receive some personal gain.

Stage 5: VO Formation (b) — VOM sends a call for bids to the SP agents and the SP agents respond.

Here the VOM issues a call for bids to all of the SPs that are capable of providing part of or the entire services requested by the user. In response, the SP agents decide whether to bid. The three main factors that influence this decision are:

1. Does the SP agent provide this specific service?

2. Given the current workload, is it possible to provide the service when required? 3. Does the SP trust the VOM enough to form a VO with it if the bid is accepted?

Stage 6: VO Formation (c) — VOM uses the pool of received bids to form a VO to serve the end user.

Upon receiving all the bids from the SP agents, the VOM evaluates each with respect to two factors:

1. What is the utility gain or loss that it will receive if a particular bid was selected?

2. How trustworthy is the SP agent or group of SP agents (recall that a SP agent can use the capabilities of its existing VO to form a bid) that the bid comes from?

Having evaluated each bid with the above two factors, the VOM forms a VO with the most

trusted agents that will maximise its own utility.

Stage 7: VO Restructuring — Change in the VO structure.

After the VO begins functioning, suppose a new agent, offering the same services as one of the members of the VO, enters the system. This agent offers a better quality of service at a lower price and is very trustworthy, giving more utility to the VOM. At the same time the agent in the VO that provides the same service decides to stop providing the service. The VOM has a need to fill this vacant space in the VO. Unaware of the characteristics of the new agent, the VOM requests a bid from this unknown agent, and when it receives the bid it evaluates it with respect to utility gain/loss and trustworthiness. However, since the VOM has not interacted with it before, it will not be able to accurately judge the trustworthiness of the new SP. The VOM therefore consults other agents in the system to develop an assessment of the reputation of the unknown agent, and uses it to calculate its trustworthiness. Assuming this is adequate, the existing member of the VO is replaced with this new agent, resulting in a more trusted VO.