That's mostly incorrect. A SLR is primarily defined by having an optical path via mirror and prism from the lens to the viewfinder and that the mirror is switched out of the light path to the film/sensor when the photograph is taken, blanking the viewfinder during the exposure. That is the reflex part of SLR.
The S5 IS has an electronic viewfinder and the picture displayed is read off the sensor. There is no optical path and no mirror in the system.