Abstract
If we consider a query involving multiple domains, such as ``find all database conferences held within six months in locations whose seasonal average temperature is 28{$^çirc$}C and for which a cheap travel solution exists'', we note that (i) general-purpose search engines fail to answer multi-domain queries and (ii) specific search services may cover one of such domains, but no general integration framework is readily available. Currently, the only way to treat such cases is to separately query dedicated services and feed the result of one search as input to another, or to pairwise compare them by hand. This paper presents NGS, a framework providing fully automated support for cross-domain queries. In particular, NGS (a) integrates different kinds of services (search engines, web services, and wrapped web pages) into a global ontology, i.e., a unified view of the concepts supported by the available services, (b) covers query formulation aspects over the global ontology, and query rewriting in terms of the actual services, and (c) offers several optimization opportunities leveraging the characteristics of the different services at hand, based on several different cost metrics.