The ReportElement class and subclasses are used to model the report in the ReportDesigner. Every graphical element (Labels, Fields) and non-graphical element (Functions, Datasets) building the report structure are subclasses of org.pentaho.reportdesigner.crm.report.model.ReportElement.
The report elements form a tree structure, and every report element inherits the capability to contain an unlimited number of child elements.
Some elements like org.pentaho.reportdesigner.crm.report.model.dataset.DataSetsReportElement explicitely check to contain only a certain kind of child elements. This limitation can be relaxed if required. The base class ReportElement does not impose such restrictions by default and it would be possible to add functions directly as a child element of a label.
Most subclasses are not shown in the diagram above.
The structure tree in the ReportDesigner reflects the element structure one by one. No additional tree model holding a copy of the structure is required.
Sample report structure and the simple class name of the underlying report element.