Validation error after entering Overview info and saving MED

Problem marker stated: cvc-complex-type.2.4.b: The content of element 'modelExtension' is not complete. One of '

{"http://org.teiid.modelExtension/2011":extendedMetaclass}

' is expected. RelationalAppearance.mxd /MyMeds Unknown Model Extension Definition Problem

Error went away once I created Property definition for a model object and "saved" the MED.