Patent ID: 8180768

Claim:
A method for extracting, merging and ranking results produced by executing multi-domain queries over “n” domain-specific search engines, said method comprising: obtaining a query and an expected number of results K by the user through a user interface; decomposing said query into “n” subqueries and associating each subquery with exactly one domain of the “n” domain-specific search engines; selecting one search engine for each said domain and one data source for each said search engine, wherein the selection of search engines used for answering the query determines also a strategy for building a combination of “n” elements among those returned as result from the “n” domain-specific search engines and data sources, wherein every combination is produced as result of n−1 join operations between elements, such that every combination comprises exactly one element for each domain; wherein the method comprises the further steps of: performing sequential accesses to each said search engine in function of the associated subquery and receiving in response results consisting of lists of elements; performing attribute-based access to each said data sources in function of results responded by search engines and receiving in response results consisting of sets of elements; computing a plurality of combinations, each of which comprising “n” elements; associating with each combination a combination score and ranking each element combination in function of the combination score; extracting the expected number of results K of combinations with the highest combination score, so as to minimize a global cost of execution of said query, the cost being a function of the costs of requests to search engines and to data sources.