trueif the current entity has the specified properties. Replacing
isntreverses the result.
entity is (entity category | entity category set)
entity is tests whether the active entity of the currently-active parse has the specified properties.
A single property can be provided, or many properties can be combined, separated by
isnt will reverse these results.
The allowable properties are
The properties can be combined by joining them with either
to yield an expression testing several properties at once.
For example, to test that an entity is an external entity with a public identifier, use
Similarly, to test that an entity is either a CDATA entity or an SDATA entity, use
do when entity is (cdata-entity | sdata-entity) ; ...