New Post: News Package - grouping data items

cw2,
Your TreeDefinitions should looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<ElementStructure xmlns="http://www.composite.net/ns/management/trees/treemarkup/1.0" xmlns:f="http://www.composite.net/ns/function/1.0">
    <ElementStructure.AllowedAttachments ApplicationName="News">
        <DataType Type="Composite.Data.Types.IPage"/>
    </ElementStructure.AllowedAttachments>
    <ElementRoot>
        <Children>
            <Element Label="News" Id="Root">
                <Actions>
                    <AddDataAction Label="Add news" Type="Composite.News.NewsItem"/>
                </Actions>
                <Children>
                    <DataFolderElements Type="Composite.News.NewsItem" DateFormat="yyyy" FieldGroupingName="Date" Display="Compact">
                        <Children>
                            <DataFolderElements DateFormat="MMMM" FieldGroupingName="Date" Display="Compact">
                                <Children>
                                    <DataElements Type="Composite.News.NewsItem" Label="${C1:Data:Composite.News.NewsItem:Title}" Display="Auto">
                                        <Filters>
                                            <ParentIdFilter ParentType="Composite.Data.Types.IPage" ReferenceFieldName="PageId" />
                                        </Filters>
                                        <OrderBy>
                                            <Field FieldName="Date" Direction="descending"></Field>
                                        </OrderBy>
                                    </DataElements>
                                </Children>
                            </DataFolderElements>
                        </Children>
                    </DataFolderElements>
                </Children>
            </Element>
        </Children>
    </ElementRoot>
</ElementStructure>