Chunking DITA Topics
By default, when a DITA map is published to an online format, each topic becomes a separate page in the output. In some cases, you may want to combine multiple source topics into one output page. For instance, you may want to combine several types of information into a single page, or you may have chosen to create many small DITA topics for reuse purposes but feel they are too small to be useful to a reader by themselves. This is referred to as chunking.
To chunk DITA topics, you set the chunking attribute on the <topicref> that
      contains the sub-topics in a DITA map. There are several values that you can set
      on the chunking attribute (for example, by-topic or
        to-content). See the DITA documentation for full details. To achieve the effects you want
      in your topics and table of contents, you may also need to set the @toc and
        @collection-type attributes on the sub-topics or container topic to suitable
      values. See the DITA documentation for details. 
You can set the @collection-type attribute on your topics using the
        Edit Properties action in the DITA Maps
        Manager. To set the @toc and @chunk
      attributes, you must open the map file in the editor and add or edit the attributes directly
      (double-click the map icon  in the
        DITA Maps
          Manager to open the map in the editor).
 in the
        DITA Maps
          Manager to open the map in the editor).
