In the base Suite, this Parameter Entity names elements that may be used inside elements that are really expected to be data characters (#PCDATA) and not to contain any of these things. In this Archiving Tag Set, this has been over-ridden to allow any phrase-level elements.
In the base Suite, this Parameter Entity is even simpler than the %simple-phrase; Parameter Entity. Note that there is no math, and there are no links. This Parameter Entity is for modeling elements that an authoring Tag Set could restrict to merely data characters (#PCDATA), but that an archival and interchange Tag Set dare not, since it needs to be able to handle the less mainstream cases.
<!ENTITY % simple-text "| %all-phrase;" >