1. A method for adapting execution of a pre-existing service that includes a predefined internal processing logic that, when executed on a processing system, is configured to process an Electronic Data Inter-change (EDI) document, the pre-existing service also including a predetermined input signature and a predetermined output signature, the method comprising: accepting the EDI document as input through a mapper service, the input to the mapper service conforming to the predetermined input signature of the pre-existing service; (a) mapping the EDI document, via the mapper service, into a plurality of intermediate documents; (b) processing the intermediate documents on a plurality of instances of the pre-existing service, to produce a plurality of intermediate results, each one of the plurality of intermediate results conforming to the predetermined output signature of the pre-existing service, each one of the plurality of instances executing processing that is based on the predefined internal processing logic of the pre-existing service; (c) reducing the plurality of intermediate results, via a first reducer service, to produce a plurality of reduced intermediate results; and (d) reducing the reduced intermediate results, via a second reducer service, to produce a final result representing a result of processing the EDI document, the result conforming to the predetermined output signature of the pre-existing service, wherein the predefined internal processing logic of the pre-existing service is different from processing logic in the mapper service, the first reducer service, and the second reducer service, wherein the pre-existing service is defined independently of the mapper service, the first reducer service, and the second reducer service, and wherein the executed processing of the plurality of instances is performed without having to rewrite the internal processing logic of the pre-existing service upon which the executed processing is based.