Hi, I created a model that has a many to many relation between a table and itself. It is used to store skills. Each skill can be the parent or the child of other skill(s). I constructed an intermediate table with the ID of the child and the parent as attributes and then created a to many relationship parents to this table and a tomany relationship children to this table. Then I flattened these relationships as documented in the manual. The problem is, that when I want to add an object to one of these relationships using addObjectToBothSidesOfRelationshipWithKey () I get the following error: Skills[348] <WOApplication 'Skills'>: NSInvalidArgumentException exception occurred while handling request: *** NSMapInsertKnownAbsent(): attempt to insert notAKeyMarker I'm just beginning to work with Webobjects and I don't have any idea what the problem is. I only included the flattened relationships in my class. Hope someone can help me with this, Thanks in advance, Stef
