Estimating resource usage

A method for allocating resources of a group of resources to tasks of a group of tasks, the method comprising: forming a resource set comprising a resource record for each of the resources of the group of resources, each resource record having one or more fields representative of attributes of the respective resource; forming a task set comprising a task record for each of the tasks of the group of resources, each task record having one or more fields, each field holding data representative of an attribute of the respective task; condensing the task set by one or more iterations of the steps of: i. selecting two or more tasks of the task set; ii. adding to the task set an aggregate task record having one or more fields, each such field corresponding to a field of each of the task records of the selected tasks and holding data representative of the collective attributes of the task records of the selected tasks in those fields; and iii. removing the task records of the selected tasks from the task set; forming at least two mappings of some or all of the members of the resource set on to one or more members of the task set; calculating, for each of the mappings, a rating value dependent on the allocation of resources to the or each aggregate task in that mapping; comparing the rating values of the mappings; and selecting one of the mappings for further processing in dependence on the result of the said comparing step.