You can also put several <exercise>s as part of an <exercises> element within a division, which is the typical way for creating a collection of exercises togther at the end of a division such as a chapter or section. The content of an <exercises> division is rather limited. It can begin with an <introduction> (perhaps a set of common instructions), followed by a mixture of <exercise> and <exercisegroup> (see Subsection 16.3.1) elements, followed by an optional <conclusion>. The sample code in Listing 16.3.1 illustrates this structure, which is rendered later as “16.4 Exercises”.
An alternative structure for an <exercises> division is to use a sequence of <subsexercises> elements, optionally preceded by an <introduction> and followed by a <conclusion>. The content of a <subexercises> element is identical to what was described above for an <exercises> element, but we emphasize that a strong rationale for using <subexercises> (as opposed to <exercisegroup>) is that a <subexercises> element can begin with a <title>, providing a clear way of organizing the <exercise>s for the reader.
Sometimes you have several exercises that should all have a common set of instructions, which is when you will use the <exercisegroup> tag. An <exercisegroup> can only be used as part of an <exercises> element or a <subexercises> element, however! The portion of this section headed as “16.4 Exercises” is produced using the code in Listing 16.3.1.
If you want the contents of an <exercisegroup> to be put in multiple columns, you can add a @cols attribute to the <exercisegroup> with value (for example) 3. The integer value of @cols must be between 2 and 6 (inclusive).
Another specialized division, <reading-questions>, can be used to house <exercise>s designed to test or guide a reader's comprehension of the material in that division. The structure of a <reading-questions> element is similar to an <exercises> element, but without the grouping options of <subexercises> and <exercisegroup>. The portion of this section headed as “16.3.3Check your understanding!” is produced using the code in Listing 16.3.2.
Reading Questions16.3.3Check your understanding!
Here is a spot to explain the purpose of these questions. It's optional, like most introductions.