I suggest to you update the WebRatio version to 7.2.4
You have to create a xsd services in the project, right click in "Services/Data Providers" -> "Add" -> "XSD provider", and in the xsd provider you have to add a xsd resource, in this resource you have to set the type as XML Schema and in the file you have to create a xsd file in the webProject this could be in the WebContent-> WEB-INF -> "descr" path into webProject
in this file you have to create the xml code similar to
And in the xsd resource you have to call this file in the File properties similar to "WebContent/WEB-INF/desc/xsd/invoice.xsd"
then you have to synchronize with right click in the xsd provider and select Synchronize XSD.. and you could see a wizard for import the entities and relationship.