EUMAS07. Sessions 3 and 4

This afternoon I'm going to attend the session about web services and another one about coordination and negotiation.

Session 3. Agents and Web Services

The room is quite empty, only 10 people. The session begins with our paper Service Discovery an Composition in Multiagent Systems. It's a review about the most common techniques and algorithms used for standard web services and agent-based solutions. A future works point had to be added, and that has been the first question: ok, a good revision, and now... what are you planning to do? :-) Well, to integrate in a model of service-oriented, agent-based, organisation-focused architecture for open systems. It sounds good but we have to begin working. Current solutions that use gateways, as WSIG or Agent2WS aren't useful. We need a common language for agents and services to live together in the same platform. Both can provide services (agent services may be more complex) and agents will be responsible of dynamic service composition.

The room is getting crowd, we're 25 people now and the second talk begins. There's a problem with his computer, so the chair exchanges 2nd and 3rd talks: Towards a Modular Architecture of Argumentative Agents to Compose Services. A good approach that refers to services in general: not web services, but services provided by agents that form a virtual organisation. The classify the demands according to different dialog types (information-seek, negotiate...). I have to check it with the dialog classification that I used in the AIWS course. They propose three models

  1. individual decision making
  2. social decision making (reasoning about the negotiation process)
  3. social interaction (controls the execution of the agreements)

(I like it) An interesting idea: to use priorities among goals and decisions. A good paper but, at the end, the negotiation of the QoS parameters is done when they have a list of winners, that is, when they have identified the service. Can be this idea be used during the discovery of the service? That would allow to discard those services that never meet the user QoS parameters.

And, finally the last one: Agent-based Framework for Web Service Composition. Agggg! his using comic font... I'm not sure that could take it seriously ;-) Well, a CBR-based solution to compose web services is proposed, so they can use semantic information to match the services (syntactic distance).I can't see the relationship with agents. Wait a moment, I have it. It's because they use a distributed solution.

And that's the end of the session, with 30 people in the room. An active session, with a lot of questions. If this is the rhythm of the EUMAS, it is going to be an interesting workshop.

Session 4. Coordination and Negotiation

After the coffee-break, the last session of the day. The first paper, Plan Coordination for Durative Tasks, is very similar to some things that I've written in my PhD. thesis. I have to read it carefully. Furthermore, Cees Witteveen is the coauthor and he has an invited talk tomorrow. I can't miss it.

The second talk, Bilateral Agent Negotiation With Information-Seeking, defines a framework to argumentative negotiation to an specific resource allocation case. The agents have (i) beliefs, (ii) desires, (iii) actions, that can be external communications or internal--message processing--, (iv) messages, (v) commitments to beliefs, desires and dialogs, (vi) action rules--actions, preconditions, constraints and consequences--, (vii) an evaluation mechanism to determine agent's intentions and (viii) preferences as priorities over actions. They use protocols for 2 types of dialogs: for information-seeking (query and response) and negotiation( offer, accept and reject). And the permissible messages, the turn taking and the order in the messages are defined for both. After the model is exposed, he shows how they can solve the resource allocation problem with this technique, but there're some cases without a soloution (cycles or agents that not need anything) because the negotiation process is blocked by self-interested behaviours of the agent.

The third paper is Teamwork Coordination for Vehicle Routing Problem and tries to find the simplest global decision that produces the max. global utility. They solve it using statistical methods from IR (maximum entropy). Sometimes, the utility is obtained not by one action, but by a sequence of actions. Furthermore, some immediate good actions for an agent can be bad for the global final utility, so they have to be punished asap.

Another article about traffic conditions is Anticipatory Vehicle Routing Using Delegate Multiagent Systems, which tries to anticipate and avoid congestions. the road is modelled as a graph where the nodes are the road junctions. Each node has one infrastructure agent and each car a vehicle agent. Before the car arrives a node, the vehicle sends exploratory ants, which ask infrastructure agents for the estimated time for their part of the route. Hundreds of ants can be sent by different vehicles. Intention ants are sent to tentative book a route. The booking have to be refreshed continuously (booking decay). Interesting solution, but with a lot of problems. The most important one is the fairness: I can book every possible route, so the estimate traffic can be faked.

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EUMAS07. Sessions 1 and 2

Well, I'll summarise some interesting talks that I've seen this morning. In general, all participants seems to be interested in the presentations: a lot of questions that the chair has to interrupt to maintain the session on time. I like it, more that the one in CAEPIA, in Salamanca, some weeks ago (I talked about that).

I've attended two sessions: one about trust and reputation and the other about organisations and institutions. As I twittered, the first speaker in the trust session hasn't appeared, so I had the opportunity of see an interesting speech about agents with hair. You'll understand that when you see the pictures :-).

A Common Basis for Agents Organisations in BDI Language.
(Also knows as hairy agents :-) Defines a basic agent as a tuple <S, SP> where S is the state and SP the behavioural specifications. And now they extends the state S with the content (Ct) and the context (Cx) of the agent. With this approach, is interesting to see how two agents intersect or how agents can be embedded into others, allowing us to define organisations.

After this paper, we continue in the trust session with the following two talks.

Supporting Experimentation for Trust Models in Virtual Organisations: TOAST

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EUMAS07. Invited talk Leila Amgoud

The EUMAS '07 begins with the invited talk of Leila Amgoud titles "Modelling Negotiation Dialogs Using Argumentation".

At the moment, it's been a very basic talk explaining what's negotiation between autonomous agents. After explain what negotiation is, she talks about the approaches to the negotiation process: game theory, heuristics and argumentation based approaches.

Game theory
As a branch of economics, assumes perfect rationality (all information is know), not an actual case. It not says anything about how the utility function is calculated and the agents can only emit proposals.

Heuristic-based
Agents don't know each other preferences, but they only exchange proposals and the preferences of each agent are fixed.

Argumentation-based
We can influence the preference relation of other agents, because we interchange proposals and arguments to "convince" the other agent.
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Now she continues explaining things about argumentation. Differentiates between two types of arguments: epistemic and practical. The former supports beliefs and is used in deductive reasoning, whereas the latest is based on proposals and is used in abductive reasoning. It's explaining basic things again (attacks, conflict-free sets...). Arguments can be credulitily or skeptically accepted or rejected. To the argumentation process take into account only the skeptical ones or the rejected to order the offers.

And now.... begins the interesting part: how to use argumentation in negotiation processes (it has taken her 40 min.!!)

She defines 3 protocol classes, but I hardy can read the slides.

... and 3 types of strategies depending on

  1. which offer/proposal to send/accept (the most used one)
  2. which argument to send

Well. this where the important part of the conference and she have used just 2 slides :-( Instead of explaining the strategies, she's continuing with an example. She compares one example without argumentation. The agents can be jammed, but the problem is solve if they can argument about their preferences (obviously).

The problem is if an optimal solution can be reached quikly. But I thing that this is not too importal. Actual life is full of non-optimal negotiations, but good enough ones. She says that they ¡'re looking for a metamodel of decision making and a general model for allowing multiattributes negotiations.

And.... that's all, folks. Some questions and we'll run for the next session. By, then.

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