A Pattern

We propose a pattern for the design of services such as this. The pattern is as follows:

• We call the location constrained service the ``Primary Service''

  The primary service is presented as a hosting service, with a specialised control API. The standard control interface is not available. Instead, a customized interface is made available.

• The operations performed by the service consumer are encapsulated in a different service interface.

  This service interface is called the ``Back End Interface.'' The consumer of the primary service must itself supply a service which implements this interface. This service is called the ``Back End Service.''

• The Primary service determines where its consumers are to be run, in its hosting service.

  The primary service offers a specialised Control Interface, allowing the consumer to define the back end service, and the local resources it requires to run. The definitions include the constraints under which the back end service will be created. In general, constraints will be loose enough to allow the service to optimse deployment.

• The primary service service is contracted normally, i.e, a Warrant is provided to the consumer by some mechanism.

  This warrant allows access to the control elements of the service, and is the warrant for the ``Primary Contract''

• All Hosting charges are reflected according to the Primary Contract.