Astro Mosaic uses Sesame service for resolving name (http://cds.u-strasbg.fr/cgi-bin/Sesame). When a name like m101 is written into target input box, a query is sent to Sesame server to resolve the name. As a result Sesame server will return an XML page that contains target RA/DEC coordinates among other things. Sesame is actually an interface to other name resolvers: Simbad, NED and VizierR.