The Getting Started section at the top of the NAVBAR holds a very important piece of information, not just for beginning users but for all taggers, namely, what is the root element of this schema?

Figure 4. JATS root element

Here is the similar root element section for the STS (ANSI/NISO Z39.102-2017, STS: Standards Tag Suite;) Tag Library, showing multiple root elements possible:

Figure 5. STS has two possible root elements