Outputting a keyword hierarchy in XML

With Tridion 2009 we saw the introduction of hierarchical keywords - aka Taxonomy, aka Intelligent Navigation - and with it a whole new world of possibilities for content classification.

However, in some cases, you really don't want all the intelligence around it and would much rather have just an "old style" xml hierarchy. If you tried this yourself, you probably figured out by now that the keyword hierarchy doesn't look so... hierarchical when viewed through the API. Not at all.

It looks rather flat.

I had to write a template recently with some information about every keyword in the hierarchy (including its metadata) for a site navigation, and keeping the keyword "parent/child'' relationships.

Here's how can you do it.

Category Navigation = engine.GetObject(NAVIGATION_CATEGORY) as Category;
using (MemoryStream ms = new MemoryStream())
{
    XmlTextWriter w = new XmlTextWriter(ms, new System.Text.UTF8Encoding(false));
    w.Indentation = 4;
    w.Formatting = Formatting.Indented;

    w.WriteStartDocument();
    w.WriteStartElement("Navigation");
    log.Debug("/Navigation created");

    Filter filter = new Filter();
    filter.Conditions.Add("Recursive", false);
    foreach (XmlNode RootChildren in Navigation.GetListKeywords(filter).SelectNodes("//*[@IsRoot='true']"))
    {
        Keyword RootKeyword = engine.GetObject(RootChildren.Attributes["ID"].Value) as Keyword;
        log.Debug("Generating XML for keyword " + RootKeyword.Title);
        w.WriteStartElement("Item");
        w.WriteAttributeString("ID", RootKeyword.Id);
        w.WriteAttributeString("Title", RootKeyword.Title);
        if (RootKeyword.Metadata != null)
        {
            WriteKeywordMeta(RootKeyword, w);
        }
        WriteChildrenXml(RootKeyword.Id.ToString(), w);
        w.WriteEndElement();
    }
    w.WriteEndElement();
    w.WriteEndDocument();
    w.Flush();
    w.Close();

    package.PushItem(Package.OutputName, package.CreateStringItem(ContentType.Xml, Encoding.UTF8.GetString(ms.ToArray())));
}

And the recursive "WriteChildrenXml" method would look more or less like this:

private void WriteChildrenXml(String RootKeywordId, XmlWriter writer)
{
    Keyword ParentKeyword = _engine.GetObject(RootKeywordId) as Keyword;
    Filter filter = new Filter();
    filter.Conditions.Add("Recursive", false);

    foreach (Keyword ChildKeyword in ParentKeyword.GetChildKeywords(filter))
    {
        writer.WriteStartElement("Item");
        writer.WriteAttributeString("ID", ChildKeyword.Id);
        writer.WriteAttributeString("Title", ChildKeyword.Title);
        if (ChildKeyword.Metadata != null)
        {
            WriteKeywordMeta(ChildKeyword, writer);
        }
        WriteChildrenXml(ChildKeyword.Id.ToString(), writer);
        writer.WriteEndElement();
    }
}

Nuno