Section 6.2 Familiarize yourself with the RELAX-NG schema
From the section on RELAX-NG schema in : “A schema is a set of patterns which describe how the elements of a language may be combined. The PreTeXt vocabulary is described by a RELAX-NG schema”.
As you experiment, you should start getting used to the “RELAX-NG schema.” If you do not follow the schema, your PTX code may not compile correctly, and even if it does compile correctly, it may not do so after an update to the
A decription for the RELAX-NG schema can be found at
http://mathbook.pugetsound.edu/doc/schema/. For instance, if you select the element
<example>in the left-hand column, you will see lists of elements under the headings “Content model elements” and “Included in content model of elements.” The former list contains the elements that the
<example>element may contain, and the latter contains the elements in which the
<example>element may be contained.