First, create a page where you'll store all of these notes and re-usable components. Then use the conref tag on the elements you want to pull in the re-usable content.

Suppose the file where you store the re-usable component is called notes.dita with a topic id of "topic_123". On this page, you might have something like this:

  <topic id="topic_123">
   ...
  <note type="note" id="bolt_warning">Don't overtighten the bolts, as it may cause stripping.</note>
 

On the page where you want to re-use the content, use the conref element like this:

  <note conref="notes.dita#topic_123/bolt_warning"/>
 

Sponsored content

In other words, use the file name#topic_id/element_id.

Conref of table content

If you're "conrefing" a table element, you have to include all of the table elements, like this:
   <table conref="notesdita#topic_123/samptable">
    <tgroup cols="2">
     <tbody>
      <row>
       <entry/>
      </row>
     </tbody>
    </tgroup>
   </table>

In this case, the ID of the table I'm re-using is samptable.

Conref ranges: Including ranges of sibling content

Sometimes you need to insert a range of elements. For example, suppose you have several paragraphs or list items. Rather than using multiple conrefs, you can instead use a range. The conref range will grab all items that are siblings.

To insert a range, you need to add an item to the first item and the last item. Here's an example:

<glossdef><p id="ot_first">The open toolkit is what processes your DITA files to transform them into webhelp, pdf, and other outputs.</p>
        <p>There are other processors besides the OT that can achieve similar results.</p>
        <p id="ot_last">OxygenXML does use the Open Toolkit to do its processing, but xMetaL uses another processor.</p>
    </glossdef>  

And here's the page where you insert the range. This is a table entry element:

<entry><p conref="glossary/ot.dita#opentoolkit/ot_first" conrefend="glossary/ot.dita#opentoolkit/ot_last"/></entry> 

You just start the conref and add a conrefend element that refers to the last item in the conref range that you want to pull over.

Conkeyref: Conrefs using keyrefs

conkeyref is similar to conref except that instead of referring to files, you refer to keys to include the target content.

example:

<keyref keys="argument" href="argument_acme.dita">

There's a paragraph in this topic with an ID of opener that I want to re-use.

I could reuse the paragraph with a conref like this:

<p conref="argument_acme.dita#topicid/opener"/>

However, sometimes when you have multiple outputs, you may want opener to pull from different files depending on the output. For example, you may have an opener for product A that differs from product B. Product A's map may point its argument key to argument_acme.dita, while Product B may point its argument key to argument_beta.dita.

To implement the conref using keys, you use conkeyref, like this:
<p conkeyref="argument/opener"/>