Task: Define Agent Decisions based on Trust Values
Define which decisions agents make depending on the trust value of potential interaction partners.
Purpose
For agents to make use of the trust values supplied by the trust values, their decisions should be based on the semantics of the values.
Relationships
InputsMandatory: Optional: External:
  • None
Outputs
Main Description

Agents make a number of important decisions that can be based on trust values:

  • Which agent to interact with
  • Which precautions to take when interacting with an agent (such as checking the result of a computation, specifying more exact conditions in the contract, etc.)
  • Whether to regard the result of an interaction in other decisions (e.g., when requesting data from sensors)
  • How the system will probably behave in the future

The system designer has to define how the agents will behave when confronted with different trust values in these situations. Often, it will be possible to make binary decisions based on a threshold, but determining this threshold can be non-trivial. In other cases, the exact semantics of the trust value need to be known to allow a staged reaction in different situations and react appropriately.

The result of this task will be an updated agent architecture description that captures the choices and their relation to trust values.

Steps
Identify agent decisions influenced by trust values
Not all decisions an agent makes are influenced by trust values. Use the trust model and the requirements documents, as well as the sources of uncertainty identified earlier to identify those decisions that need to be made under uncertainty and that thus benefit from trust values. If decisions are identified that are not yet covered by the trust model, it might have to be redefined or an additional trust model for a previously unidentified source of uncertainty has to be introduced.
Define the different choices an agent has in each decision

In many cases, agents only have a limited set of options to choose from in a decision. If that is the case, these possible choices should be catalogued and their consequences and the circumstances under which they are useful should be identified.

Should the decision have an arbitrary number of possible outcomes (e.g., when the agent has to decide on a value for a continuous variable), identify the function that maps input data to the variable.

Map ranges of trust values or thresholds to the different choices

If a set of discrete choices has been found, relate the trust values to the choices by identifying how the trust value influences the decision and which ranges of trust values warrant which choice. If additional factors are considered in the decision, identify the correlation between trust values and these factors. It is often useful to define the decision procedure formally to avoid ambiguity and to enable formal analysis.

In case a function is used for the decision, augment the function definition by including the trust value as an input.

Properties
Multiple Occurrences
Event Driven
Ongoing
Optional
Planned
Repeatable