Virtual clinical laboratories are linked using horizontal reasoners, and lab test results are then linked to clinical databases using vertical reasoners.

In the vertical reasoning phase, in addition to comparing patient data, we can also compare images to determine whether we have found similar patient records. Therefore, content-based image similarity retrieval becomes a part of the vertical reasoning. Depending upon the application domain, image similarity can be based upon shape, color, volume or other attributes of an object, spatial relationship among objects, and so on.