1. A method of managing a product supply chain based on product unavailability or product sourcing location unavailability by establishing a product availability check framework between at least two product sourcing locations in the supply chain, comprising: providing a computer processor and computer hardware to define a plurality of inclusive rules, each inclusive rule specifying at least one of a location and a product to be checked for availability; and to define a plurality of exclusive rules, each exclusive rule specifying at least one of a location and a product which is excluded from being checked for availability; wherein the plurality of rules are provided to the processor for selection by the processor within a product availability check or location availability check procedure executed by the hardware and the processor, and further wherein at least one exclusive rule of the plurality of exclusive rules comprises at least one indication which is representative of at least one time period in which the exclusion of the at least one location or product specified in the respective exclusive rule is valid; and managing the supply chain according to the execution of the availability check procedure to maintain a chain of supply when at least one product or at least one product sourcing location is unavailable.