The cwu accessor is used to set the current working URI of an idoc execution.
All reletive URI are resolved against the current working URI. This primative operation is built into the DPML language.
cwu can be called with a canonical URI document using the curi: scheme for
dynamic assigment of the CWU.
If the operand is omitted then the CWU is set to null and no relative URIs can be resolved.
This is useful when calling scripts that will determine their own CWU if one is not specified.