In a method of managing an inventory of service resources, a plurality of criteria characterize service resources. The inventory of service resources is divided, based on the criteria, into plural elements, each comprising an exclusive subset of the service resources sharing common criteria. A plurality of groups is also created. Groups aggregate those of the elements that have at least one common criterion value. Groups and elements are offered for sale by the service provider. Elements belong in general to several groups. Service resources are, e.g., travel service or leisure resources such as airplane seats and hotel rooms. Customers or travel agents book in an element or in a group. The invention allows maximizing inventory availability while bookings are done by customers, on the basis of a specific request (in an element) or a more indefinite request (in a group). A specific inventory item is attributed later, i.e., at check-in.