Thursday 30 April 2009

Make goals known at outset?

Why not make agents' goals (as well as the initial system-wide resource allocation and resource-goal fulfils plans, as is currently being done) known at the outset, given that agents declare their goals freely during negotiation anyway?

Testing the time-stamp negotiation policy

Compiled and started tested the MARA (mutiagent resource allocation) time-stamp negotiation policy. Seems to be working fine except that agents seem to accept two or more requests/proposals for the same resource simultaneously... instead of delaying. Problem! Looking into it now.

The importance of stupidity in scientific research

"... What makes it difficult is that research is immersion in the unknown. We just don’t know what we're doing. We can’t be sure whether we're asking the right question or doing the right experiment until we get the answer or the result..."

Good article summarising what PhDs are about.

Saturday 25 April 2009

Revising the 'argmas09' negotiation policy to use time-stamps

Started revising the 'argmas09' negotiation policy to use time-stamps such that beliefs of agents are accumulated only rather than revised (i.e. added/removed). The case for investigating into trust (for verifying arguments/utterances of agents) and related matters seems more interesting than first anticipated.

Thursday 23 April 2009

Progress So Far

eumas 07 ('revised') paper
  • Agents have beliefs and desires over single resources, as well as (retractable) commitments to other agents over beliefs, desires and dialogue. Attaining any one of its desired resources achieves the agent's overall goal.
  • (Request-Response) Information-seeking dialogues are used to communicate beliefs and desires.
  • (Request-Response) Negotiation dialogues are used to swap single resources. An agent accepts a request to exchange resources if the resource to be received is one that it desires.
  • The negotiation policy is not complete. The case for reasons/argumentation to accompany the negotiation is put forward.

eumas 08 ('revised') paper / ('modified') implementation
  • The goal of an agent is to obtain a certain fixed set of ("needed") resources (one at a time).
  • Negotiation only (i.e. a Request followed by Accept or Refuse). No separate Information-seeking.
  • A request of an agent is to be given a certain resource by a certain agent, with an (optional) accompanying reason (i.e. "I need the resource and do not have it").
  • An acceptance has no accompanying reason. An agent accepts a request (to give away a resource) if it has and does not "need" the resource.
  • A refusal may have an accompanying reason, i.e. "I do not have the resource", "Some other agent has the resource", "I have but need the resource".
  • Two negotiation policies are compared for "effectiveness" and "completeness" - one in which agents exchange reasons, and one in which they don't. Both policies are complete but providing reasons improves "effectiveness" of an agent achieving its goal if possible or failing if not possible.
  • (See 'readme' file of 'eumas08modified' implementation for implementation notes.)

aamas 09 ('revised') paper / ('modified') implementation
  • Each agent has a (/one) named goal. Goals are fulfilled by single resources. A certain goal may be fulfilled by a choice of different resources. A certain resource may fulfil a choice of different goals.
  • Agents do not necessarily share "plans" (as to which resources fulfil which goals) at the outset. These are communicated (partially, as necessary) during negotiation.
  • Negotiation only (i.e. a Request followed by Accept or Refuse).
  • A request of an agent to another is either to be given a certain resource or to swap (single) resources, with (optional) accompanying reasons/arguments (i.e. a mixture of "needsToObtain", "notNeeds", "useful").
  • An acceptance has no accompanying reason. Agents agree to give away a resource if either they do not "need" it or they receive in return a resource of equal value.
  • A refusal may have accompanying reasons/arguments (i.e. a mixture of "needsToRetain", "notHas") plus useful additional information (i.e. alternative plans).
  • Two negotiation policies are compared for "effectiveness" and "completeness" - one in which agents exchange reasons/arguments, and one in which they don't. The policy that makes use of reasons/arguments is demonstrated to be more (but not fully) complete and more effective in identifying solutions. No formal proofs.
  • (See 'readme' file of 'aamas09modified' implementation for implementation notes.)

argmas 09 (in progress) paper / implementation

Pseudo-algorithm Explaining Argument Evaluation Implementation

(Procedural) Pseudo-algorithm explanation of my (Declarative) Prolog Argument Evaluation Procedure:
Given claim C;
Get a backward deduced support (consisting of private facts and assumptions) S of C;
Add C to Friends;
Add all sentences in S to Defences;
Get the set AttackArgs containing all arguments that attack the assumptions of S;
Append arguments in AttackArgs to Enemies;
Repeat: For each argument AttackArg in Enemies
If AttackArg contains a Culprit,
Remove AttackArg from Enemies;

Otherwise,
Remove AttackArg from Enemies;
Get a contrary D of some non-Defence assumption A in AttackArg;
Add A to Culprits;
If D is a Friend, skip forward to Repeat;
Get a non-Culprit-contaminated backward deduced support S of D;
Add D to Friends;
FilteredS = S with all Defences filtered out;
Append sentences in FilteredS to Defences;
Get the set AttackArgs containing all arguments that attack the assumptions of FilteredS;
Append arguments in AttackArgs to Enemies;
End Repeat
Explaining the implementation in terms of the Dispute Derivation Definition, the player choice and selection function is such that P is emptied immediately whenever a sentence is added to P , such that a set S in O is only addressed if P is empty. Hence, when attacking an assumption A in an element S of O, the check whether A is in P is not required (since P is empty). So, in conclusion, the implementation need not be modified despite the changes made to the Dispute Derivation Definition.

Explaining My Multiagent Dispute Derivation Procedure

Spent the last few weeks writing about my modified admissible belief dispute derivation procedure. Except for one proof outstanding, the first draft seems done.

Sunday 19 April 2009

Individual Transferable Quotas

An article (idea) I came across that makes use of distributed negotiation and social welfare concepts:

"Iceland has not quite proved that fish can sing, but it has shown they can continue to flourish, even when hunted by their main predator, man. Central to its policy are the individual transferable quotas given to each fishing boat for each species on the basis of her average catch of that fish over a three-year period. This settles the boat’s share of the total allowable catch of that fish for the entire country. The size of this total is announced each year on the basis of scientific advice from the independent Marine Research Institute.

Subject to certain conditions, quotas can be traded among boats. Bycatch must not be discarded. Instead it must be landed and recorded as part of that boat’s quota. If she has exhausted her quota, she must buy one from another boat, though 20% of a quota may be carried forward a year, and 5% of the next year’s quota can be claimed in advance..."


(Source: The Economist, January 3rd 2009)