The H-Representation of a polyhedral set is comprised of two elements: the coordinate space in which it lives and the list of relations.

The Coordinates command returns a list of names for each dimension of the ambient space in which the polyhedral set is defined.

The Relations command returns the list of inequalities and equalities that limit the set to a subset of the ambient space.  This list will be empty in the case of the universal set, comprised of all points in the coordinate space.  The set's relations have been put into a canonical form and so this list will not necessarily match the list used to initially build the set with the PolyhedralSet command.

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

$\mathrm{p1}≔\mathrm{PolyhedralSet}\left(\left[3\le x\,10\le y+x\,x\le 10\right]\right)\;$$\mathrm{coords}≔\mathrm{Coordinates}\left(\mathrm{p1}\right)$

$\mathrm{p1}≔\{\begin{array}{lll}\mathrm{Coordinates}& \:& \left[x\,y\right]\\ \mathrm{Relations}& \:& \left[-y-x\le \mathrm{-10}\,-x\le \mathrm{-3}\,x\le 10\right]\end{array}$

$\mathrm{coords}≔\left[x\,y\right]$

$\mathrm{Relations}\left(\mathrm{p1}\right)$

$\left[-y-x\le \mathrm{-10}\,-x\le \mathrm{-3}\,x\le 10\right]$

The PolyhedralSets[Coordinates] and PolyhedralSets[Relations] commands were introduced in Maple 2015.

For more information on Maple 2015 changes, see Updates in Maple 2015.