Compact is a function that converts an expanded form of a ontology property
into its compact representation. If we are unable to compact the value then
we return the input string. This allows this function to be called safely on
an already compacted property.
Expand returns the expanded version of a value (either prop or value). If we
are unable to expand the value then we return the input string. This allows
this function to be called safely on an already expanded property.