code: public XPointerEngine setBaseURI(final String baseURI)
      {
          if (baseURI == null)
          {
              this.baseURIValue = XdmEmptySequence.getInstance();
          }
          else
          {
              this.baseURIValue = new XdmAtomicValue(baseURI);
          }
          return this;
      }
docs: Setting the base uri for the pointer resolution
  The base uri is used for xml:base calculations
  
  @param baseURI of the parent xml
  @return the XPointerEngine for fluent api usage