Planar Partition Repair takes a set of polygons and ensures that they form a valid planar partition, made of valid polygons and having no gaps or overlaps. It can be used as a validator, telling you about problems in individual polygons or in the planar partition, and also as an automatic repair tool, outputting a set of polygons that do form a valid planar partition. 

Developed by OGC this is a web-server, tomcat application that provides an endpoint that accepts GML resoponses from WFS GetFeature requests. There are limitations if you want to test more than 500 polygons (crashed the service)