%sec-opt-title-model; Content Model for an Untitled Section

The model for a section-like structure that may or may not have an initial title.
Declaration
<!ENTITY % sec-opt-title-model
                        "(sec-meta?, label?, title?, (%para-level;)*,
                          (%sec-level;)*,
                          (%sec-back-matter-mix;)* )"                >
Expanded Declaration

(sec-meta?, label?, title?, (address | alternatives | answer | answer-set | array | block-alternatives | boxed-text | chem-struct-wrap | code | explanation | fig | fig-group | graphic | media | preformat | question | question-wrap | question-wrap-group | supplementary-material | table-wrap | table-wrap-group | disp-formula | disp-formula-group | def-list | list | tex-math | mml:math | p | related-article | related-object | disp-quote | speech | statement | verse-group)*, (sec)*, (fn-group | glossary | ref-list)* )