The CleanEntities(expr) command returns an equivalent xmlTree with the _XML_Entity elements removed and replaced with encoded text.  If no entity conversion is found, the _XML_Entity will still be replaced, but with an unconverted string.

$\mathrm{with}\left(\mathrm{XMLTools}\right)\:$

$\mathrm{xml}≔\mathrm{ParseString}\left(''Capital\; \Pi \; is\; different\; than\; \pi ''\right)$

$\mathrm{xml}≔\mathrm{\_XML\_Document}\left(\mathrm{\_XML\_Element}\left(\mathrm{\_XML\_ElementType}\left(''tag''\right)\,\left[\right]\,\left[\mathrm{\_XML\_Text}\left(''Capital''\right)\,\mathrm{\_XML\_Entity}\left(''Pi''\right)\,\mathrm{\_XML\_Text}\left(''is\; different\; than''\right)\,\mathrm{\_XML\_Entity}\left(''pi''\right)\right]\right)\right)$

$\mathrm{CleanEntities}\left(\mathrm{xml}\right)$

$\mathrm{\_XML\_Document}\left(\mathrm{\_XML\_Element}\left(\mathrm{\_XML\_ElementType}\left(''tag''\right)\,\left[\right]\,\left[\mathrm{\_XML\_Text}\left(''Capital\; \Pi \; is\; different\; than\; \pi ''\right)\right]\right)\right)$

$\mathrm{xml}≔\mathrm{ParseString}\left(''The\; number\; 쾀\; is\; approximately\; 3.14''\right)$

$\mathrm{xml}≔\mathrm{\_XML\_Document}\left(\mathrm{\_XML\_Element}\left(\mathrm{\_XML\_ElementType}\left(''tag''\right)\,\left[\right]\,\left[\mathrm{\_XML\_Text}\left(''The\; number''\right)\,\mathrm{\_XML\_Entity}\left(''\#xcf80''\right)\,\mathrm{\_XML\_Text}\left(''is\; approximately\; 3.14''\right)\right]\right)\right)$

$\mathrm{CleanEntities}\left(\mathrm{xml}\right)$

$\mathrm{\_XML\_Document}\left(\mathrm{\_XML\_Element}\left(\mathrm{\_XML\_ElementType}\left(''tag''\right)\,\left[\right]\,\left[\mathrm{\_XML\_Text}\left(''The\; number\; \pi \; is\; approximately\; 3.14''\right)\right]\right)\right)$

The XMLTools[CleanEntities] command was introduced in Maple 2018.

For more information on Maple 2018 changes, see Updates in Maple 2018.