To describe the concepts of ownership and control let us add a new layer: the social layer. Now the paradigm is composed of two interacting layers, one where production takes place and another that hosts agents owning and/or controlling the production entities. Each layer can be complex or even hierarchical, but the production layer does not have social properties, whereas the social layer does. Henceforth let us call the agents that reside in the social layerSocial Grid Agents or, for the sake of brevity,
Social Agents. This is shown in Fig. 3-5.
Agents in the social layer can own or control or use none, one or more production agents. A social agent should also be able to exchange and trade the use of, or the services produced by, the production agents it controls. This allows our social and economic paradigm to exhibit behaviour such as the purchase of services, therent of production agents and theexchange of ownership of one or more related production agents. Let us propose that these relations between social and production agents can be of ownership, control or usage:
• Ownership: when social agents own production agents they have complete con- trol over them; they can sell, rent or donate them; they can set access rights for controllers and users and they can set policies to regulate the production process.
• Control: when social agents control production agents, they have partial control over them (that may have been delegated by an owner); they can set access rights for users and set (possibly a sub-set) of production policies.
• Usage: when social agents use production agents they can access only the services that they were granted by a controller or an owner.
Multi-modal relations
To better understand, design and implement transactions such as rent, purchase and donations it is useful to propose different modalities in which the above mentioned relations can relate both to time and the space of the resources.
Relations might have different time modalities such as:
• Absolute: Either true or false, especially as a logical attribute of ownership relationships.
• Token-based: to allow the submission of a certain number of requests to a pro- duction agent, especially for simple service rental scenarios where a social agent buys (or receives) a given amount of service execution rights on a production agent that it does not control or own.
• Deadline-based: to allow the control of a production agent for a given amount of time, especially for more complex service rental scenarios where a social agent acquires temporary control of other production entities to engage in the execution of a complex service.
• Time slot-based: to allow the use of the services of another agent until the allowed amount of time has been used, especially for reserving processing and storage services.
• Combined: to allow modalities to be combined together: e.g. token-based and deadline-based modality might be combined to obtain a modality where tokens have expiry dates while time slot-based and deadline-based modalities might be combined to obtain a ”perishable” reservation on computational and storage services.
Relations might also be allowed with regard of the controlled resources. These concepts relate to the allocation modalities examined further in section 3.2.6. They can be roughly divided into:
• Complete: give ownership and control over all resources controlled by the agent over the specified period of time.
• Partial: give ownership and control over a part of all the resources.
It is clear that some form of constraint has to be provided over the modalities with which each of the actors sets the rights of the others. If no such control is provided
there may be cases in which agents gain control of other agents in an unforeseen way. As an example, let us suppose that an owner O grants control to an agent C
to one of his production agents P, with a deadline modality that expires at a date
T. As the controller can set any kind of access rights for the user it is possible for the controller to set absolute rights to a user U. These rights, being absolute, will outlive the range of time in whichC is allowed to controlP. To avoid such problems one might constrain the setting of the access rights as follows.
• For owners: owners might be allowed to set any kind of access rights and they might be enforced directly.
• For controllers: the access rights that controllers enforce might depend on the access rights they have, for example:
– Absolute modality: enforced directly.
– Deadline modality: If the controller has Deadline modality access rights, its commands change in the following way.
∗ Absolute modality → Deadline modality.
∗ Deadline modality → Deadline modality with an expiry date that is the minimum between the controller’s and the target’s settings.
∗ TimeSlot modality → TimeSlot and Deadline modality.
∗ Token modality → Deadline and Token modality.
– Token modality: token modality is a way for controllers to grant execution rights to users, and thus is usually granted to users and not controllers. Should the case arise of tokens being granted to controllers they are treated as if they are users: Token modality → Token modality.
• For users: users might not be able to set any access rights.
The above simple modalities are powerful enough to describe some interesting basic topologies of ownership and control.