To write the Relations element (Rl) in the index.

§1. A four-column table of relations.

void RelationsElement::render?Usage of RelationsElement::render:
The Periodic Table - §4(OUTPUT_STREAM, index_session *session) {
    localisation_dictionary *LD = Indexing::get_localisation(session);
    tree_inventory *inv = Indexing::get_inventory(session);
    InterNodeList::array_sort(inv->relation_nodes, MakeSynopticModuleStage::module_order);

    HTML_OPEN("p");
    HTML::begin_plain_html_table(OUT);
    HTML::first_html_column(OUT, 0);
    Localisation::italic(OUT, LD, I"Index.Elements.Rl.NameColumn");
    HTML::next_html_column(OUT, 0);
    Localisation::italic(OUT, LD, I"Index.Elements.Rl.CategoryColumn");
    HTML::next_html_column(OUT, 0);
    Localisation::italic(OUT, LD, I"Index.Elements.Rl.FromColumn");
    HTML::next_html_column(OUT, 0);
    Localisation::italic(OUT, LD, I"Index.Elements.Rl.ToColumn");
    HTML::end_html_row(OUT);
    inter_package *pack;
    LOOP_OVER_INVENTORY_PACKAGES(pack, i, inv->relation_nodes) {
        text_stream *name = Metadata::optional_textual(pack, I"^name");
        text_stream *type = Metadata::optional_textual(pack, I"^description");
        if ((Str::len(type) == 0) || (Str::len(name) == 0)) continue;
        HTML::first_html_column(OUT, 0);
        WRITE("%S", name);
        IndexUtilities::link_package(OUT, pack);
        HTML::next_html_column(OUT, 0);
        if (Str::len(type) > 0) WRITE("%S", type); else WRITE("--");
        HTML::next_html_column(OUT, 0);
        text_stream *term0 = Metadata::optional_textual(pack, I"^term0");
        if (Str::len(term0) > 0) WRITE("%S", term0); else WRITE("--");
        HTML::next_html_column(OUT, 0);
        text_stream *term1 = Metadata::optional_textual(pack, I"^term1");
        if (Str::len(term1) > 0) WRITE("%S", term1); else WRITE("--");
        HTML::end_html_row(OUT);
    }
    HTML::end_html_table(OUT);
    HTML_CLOSE("p");
}