KMeans can be validated with ClusterCenteroidEvaluator
But KMedoids and KernalKMeans can not: It passes operator IO validation, but when executed fails in ClusterCenteroidEvaluator with 'The operator needs some input of type centroid based cluster model which is not provided'
you are right. We are currently revising the interfaces for the clustering methods and actually found some other drawbacks with the current interface definitions. So thanks for pointing out this issue. We will try to sort this out until the next release.
How to load processes in XML from the forum into RapidMiner: Read this!